While the first version of the Opus+ software was still under development it was necessary to run musical test sequences generated by the neophyte code. Links to these are shown below along with the date the tests were run. Many of these sequences are examples of 'found music'; they have not been edited or altered by human hand in any way, and where they have these human edits are described in full.


'The Hydra Series' is a collection of four pieces each around three minutes long derived from a single Opus+ composition. This work took place over five days at the end of May 2010 and demonstrates how Opus+ can provide base musical material which can be arranged and utilized in a variety of ways. The source material was generated in July last year as part of a test sequence for an Opus+ component that writes musical material in sections, and was chosen nearly a year later randomly - literally without thinking - while exploring the capabilities of Apple Logic Pro 9 to quickly load some example MIDI data into a project. Producing several different arrangements of this single piece provided a convenient way of exploring the new Pro 9 software and prompted the question of just 'what is a musical composition?'; working on Opus+ has brought this question into focus of late. For the record, orchestration and arrangement of all four hydra pieces adhered to our rules on 'found music' as described in our FAQ

Hydra:Rhythm is technically the simplest arrangement of hydra and uses the generated drum track entirely unedited as material for a tabla voice, and this is accompanied by traditional Indian Sitar, Indian flute and an Indian Oboe. The emphasis here is on the rhythmic qualities of the generated material, which seem to fit naturally with these instruments.

Hydra:Duo is an arrangement for piano and clarinet and falls into the category of 'the avant-garde'. The tempo changes are fairly extreme, and many of the generated phrases are rendered almost unrecognisable by the process of deletion - notes are muted to increase space within the piece. There is also a gradual increase in the octavation of the piano parts towards the end to help build a crescendo which moves to a slightly overly-positive statement of themes at the very end.

Hydra:Plenitude is a rock mix of the hydra material for guitar, bass, drums and wurlitzer using the new guitar cabinets and FX pedals that come with Pro 9. I think the drummer was, as they say in common parlance, "off 'is 'ead" in the studio here - the end result is somewhat intense! :-)

Hydra:Profusion is an orchestral arrangement which, while it might not be 'good' per se, is at least 'convincingly bad'. Some parts are not quite as bad as others, particularly the introductory phrase in the clarinet starting on bar 5, and the section between bars 37 to 45 where the music slows and then picks-up with truly pompous sounding tympani parts.

Hydra:Raw is a 'vanilla mix' of the material as generated by Opus+; after importing the generated MIDI the original instruments are kept, their relative volumes are adjusted, the parts are 'humanized' (a transform provided in Pro 9 which randomly perturbs MIDI information slightly to imitate the velocity and timing errors of human performers), they are panned across the stereo image and placed into a simple reverberant environment to give some semblance of natural staging. This is provided by way of a benchmark to compare the other arrangements for congruence with the original, so it is easier to hear which elements were contributed to the 'composition' by Opus+, and which resulted from the processes of orchestration, arrangement and production in Logic Pro 9. All versions of Hydra along with the original score as a PDF are available below.

Music for Prepared Pianist

'Music for Prepared Pianist' was originally generated as two separate pieces for two guitars and acoustic bass, as part of a test sequence for a new Opus+ component that works with caches of chords and rhythm patterns; generating voice parts by re-using chord sequences at different points in the composition and slicing horizontally through sets of chords in different ways, and combining these with a variety of rhythm patterns drawn from the cache. New material is introduced into the cache in addition to, or replacing, existing material with varying degrees of probability. The composition at this point has a clearly defined harmonic integrity but lacks a certain musical variety. Another Opus+ component then writes passing notes at random points throughout the piece constrained by a set of parameters controlling their number, pitch and duration.

While arranging this piece the harmonic interest was so strong that having the three voices with different timbres detracted from the listener's experience, so we decided to mix this simply with all voices playing on a Bosendorfer grand piano. Later we realized the piece requires three hands, so it might be played as a piano duet, with one pianist using a single hand, or we could stitch an extra arm on the pianist 'preparing' them for the performance - while John Cage interferes with his pianos we don't spare our pianists! :-) The original MIDI and an MP3 mixed in Apple Logic along with the original score as a PDF are available below.

Strange Beeps

'Strange Beeps That My Ears Hear' is a short piece which vaguely reminds one of the backing for a Captain Beefheart track in the style of 'The Thousand and Tenth Day of the Human Totem Pole' on the most excellent album 'Ice Cream for Crow'. Not of course in the instrumentation or in recording quality - it's not even close - but in the way that it stumbles and jerks clumsily as a musical piece. Even if you disagree with this comparison, as a composition it sounds purposeful as if it was written by a human composer, albeit not a very good one! This was first created on 13th November 2007.

Here is also a re-mix of the earlier version of 'Strange Beeps That My Ears Hear' but this has substantial changes from the original composition generated by Opus+. Firstly the entire piece is copied and repeated, because it is quite short and we found that it loops well, and an additional instrument was added - the tuba - and it shares parts of the bass line. In fact the bass part contains chords, which effectively means that, given that the tuba cannot play chords, we've added an entire tuba section! At one point a beautiful figure is enhanced with an additional 5th to the existing chord, and some voices are dropped an octave - so in short this mix diverges from the original generated material. The result is however, utterly top banana!!! The original MIDI and MP3 along with a re-mix together with the original score as a PDF are available below.

Forget Shakti

'Forget Shakti' is one of the first pieces generated using a technique which combines random fragments of music, each of which can be transformed in a finite number of ways. Purely by coincidence the result was a distant reminder of the work by the superb and utterly peerless band Shakti - hence the name - a play on a recent album entitled 'Remember Shakti'. This work was originally produced on 10th October 2006.

This was remixed on 19th June 2009 and uses unusual acoustic instruments from around the world to produce an interesting rendition of the original.

Neutron Duet

This piece called 'Neutron Duet' was composed during the work sponsored by Sussex University with Richard Durrant for the RopeTackle arts performance. It required the development of a serialism notator that composes according to the rules described by Arnold Schoenberg. This duet for woodwind and guitar is yet more test output and follows a very strict version of serial procedure using a 12 note row, and the usual three derivative rows: retrograde, inversion and retrograde-inversion that together form the four base rows. The 'strict' algorithm used chooses one of the four base rows at random, decides whether to modulate this row by between 0 and 11 semi-tones at random, and then consumes each pitch from the modulated row in turn. Each musical element in the duet is selected in time-series order independent of the actual voice sounding the pitch, and where multiple music elements start sounding at the same time, they are ordered at random. As each pitch is set, there is an opportunity to choose and set its octave between the minimum and maximum for that voice, again at random. Only when the current row has been fully consumed, can the next row be selected and the whole procedure repeated until the composition is complete.

'Neutron Duet' is so named because it was generated using data showing asymmetries within neutrons from the Insitute Laue-Langevin in Grenoble measuring the Electric Dipole Moment (EDM). This data was supplied by Professor Philip Harris from Sussex University and forms the basis of every compositional decision taken within this piece.

African Harmony

'African Harmony' was generated while working on notation components that write vertically integrated harmonies across several voices in sections, by storing and reusing sequences of chords and then slicing these horizontally using several different algorithms. Variety is introduced by another component which writes passing notes using another set of algorithms all constrained by parameters that can be controlled by the user. The MP3 mix has been transposed onto African percussion instruments and bubbles along quite happily; it even has something not entirely dissimilar to a cadence at the end.

Frippin 'eck

This piece 'Frippin 'eck' is the closest that any Opus+ composition has come to prog-rock so far, and it's probably impossible to play. Clive's mix sounds HUGE and immediately brings to mind some of the very best of this genre - in fact we bet that even the incomparable Mr Fripp would be pushed to play this!

In this version produced through Apple Logic the composition itself has had one gratuitous edit, where a couple of bars were moved in time, and although this technically disqualifies it as pure 'found music' it is certainly 'more-found-than-fiddled' music. Apart from this single exception, the usual rules were applied during mixing, limiting certain compositional edits, to ensure the end result was faithful to the generated composition. (These rules were first used when we re-mixed the piece Synth-Pop and are described below.)


'Stonk' is a beautiful meditative piece generated during some recent tests with Opus+ parameter settings, and its name comes from the 'stonking', almost flamenco-like, two-bar bass phrase which runs throughout. Again this is 'found music', the composition is unedited in any way, and the mix was done using Apple Logic.

Crucial to the end result was the use of humanization ; a feature in Logic which perturbs the clinical regularity of MIDI information. As an A-B listening test of the links below will show, the MIDI generated by Opus+ is so regular it's probably capable of 'aligning all the listener's brain cells to point due north'! - but this is easy to rectify if a more natural sound is required :-) There are three variables to humanisation: the note length , its velocity and its position (onset), and all these default to maximum in Opus+ generated MIDI. To humanize these imports we dropped all these variables globally on each MIDI voice by around 10%, and then invoked the 'humanize' function in Logic. Aside from this humanization, we chose the instrument voices, dropped the overall tempo slightly, and arranged for a slow fade-out at the end.

Synth Pop

'Synth Pop' originally produced by Opus+ completely artificially on 15th November 2007, is twenty bars in duration and quite simply sounds brilliant! It's a complete surprise to me just how convincing this sounds, (from a compositional perspective, not performance or production), so I took the liberty of copying and repeating the twenty bars three times to make a 2 minute pop/dance track.

On 10th October 2008 'Synth Pop' was re-orchestrated. This mix was done using the powerful editing facilities in Apple Logic, but with certain 'compositional constraints'. The rules were that new instruments could be introduced, and the original voices could be shared out 'vertically' between the new instruments; effects such as equalization, reverb, panning and echo where allowed, and it was even permissible to change the octavation of musical fragments, for example if a treble part was moved onto a bass instrument, or drop voices out for a few bars. However, tampering with the actual fragments, moving them horizontally through time, or writing new fragments were specifically disallowed; the constraints we worked within preserved the original order of musical material, so we could clearly hear its musical lineage from Opus+. Now where's my agent.... ;-)

Carved to Irritate

This piece 'Carved to Irritate' is to my ear 'abso-bloody-lutley marvellous'!!! Clive decided he needed to really learn Apple Logic properly, so as you do, he decided to take his laptop on a cycling tour of France (?!) 'to get some space to work without distractions', and after several weeks working in a tent just south of Brittany without a lot of electricity, he produced these quite astounding mixes! The compositional material is pure, unadulterated Opus+, and was produced from a recent regression test after some extensive code re-factoring. The title 'Carved to Irritate' pays tribute to an excellent Brighton band from around the mid 80's called 'Carved to a Noise', primarily because of the vicious opening drum sequence, and the way these relate to the somewhat unusual guitar parts typical of some of their work.

There are two mixes, and it's interesting to compare these to the original MIDI produced by Opus+, to get a glimpse of the sheer number of creative directions the production and orchestration process can take. The first is a 'meat-and-two-veg' rock mix quite close to the sound of the original MIDI. The second is a synth based derivative mix, which really begins to push the generated piece into a different musical category. The spectrum of creative possibilities here is huge, even without direct edits to the actual composition 'as generated'.

As a compositional experiment there is another version of 'Carved to Irritate', but this time the actual composition has been 'reconstituted' manually, using elements exclusively drawn from the original material generated by Opus+. Sometimes it is easier for a composer to respond to 'given material' than work from a 'tabula rasa'. In places it's almost as if Mr Fripp were a guest guitarist with Carved to a Noise - enough to make some people go "all knees and elbows with chameleon eyes that independently spasm." (That really is one of the nicest things anyone has said about Opus+ !).

Summer in Algiers

'Summer in Algiers' named after the book by Albert Camus, was also part of the 'experiment with order', and starts with a beautiful haunting section which relies on an interplay between the instruments that is very hard to conceive of being written by a human. It then progresses to a lovely open, free sequence that continues to the end (which might have been better finished with a gentle fade out!). Although this music is complex on the printed page, we believe that musicians with sufficient wherewithal would be able to play this reading from score, having been given enough practice time prior to performance.

This was the forth piece mixed through Apple Logic and, as a comparison with the original MIDI file shows, the orchestration in terms of the voicing’s and instruments really affects how parts of the composition are elevated. This can be heard in bar 14 where the first guitar appears to introduce a new phrase and starts to play completely across the established rhythms. In the original MIDI the effect is quite jarring, whereas in the mixed MP3 it sounds completely natural, adding space and depth.

From the Planet Gong

'From the Planet Gong' was also generated in the series of tests looking at creating music with a more ordered form using a software entity called a state-machine. As the music is written for each instrument a state-machine is used to control how repetition and variation within the piece are balanced. The result is a composition in a set of six 24 bar sections, and in all cases, the drums, bass, backing guitar and marimba all play a regular repeating pattern of some description. In the first 12 bars of each section, the lead guitar is silent to give the listener a chance to become acquainted with the pattern, and then in the next half the lead guitar is allowed free reign.

The production quality is comparatively superb as a result of going through the Apple Logic software, and we lost count of the number of Steve Hillage air-guitar impressions we had during mix-down!

Prelude for Piano

'Prelude for Piano' was created during some tests looking at the sorts of rules necessary to generate interesting piano parts. Piano compositions are notoriously difficult to write convincingly, so we examined the scores of some Bach preludes in an attempt to understand something of the musical structure, so this might guide our choice of parameters. This was an incredibly interesting exercise, and after a few runs, this piece occurred. It's not Bach, but it does have a musical theme which develops, a tune is discernable, and the piece moves and resolves in a natural sounding way. The two chords at the end were the result of a very short section consisting of a single bar where the constraints were set such that chords were certain to occur. From the pianist's perspective its level of difficulty is probably about grade 8.

This test also revealed a requirement that we improve the way Opus+ handles piano score layout. The issue has to do with piano staves, which unlike other instruments, have two voices that can move between the treble and bass staff. In any bar, the voices can swap between treble and bass, or they can both play down in the bass or simultaneously up in the treble. This means that it is possible to get 'crossed beams' (i.e. bars 2 and 11 for examples) which look untidy and are difficult to read. Work is in progress to rectify these issues as far as possible.

Tessellation Chromatix

'Tessellation Chromatix' occurred one evening during a new set of experiments using Opus+ with constraints which produce much more 'ordered' or 'regular' compositions. The idea tested here is that music is essentially about repetition at its most fundamental level. Any musical phrase repeated a few times, assuming that the phrase is short enough to be retained in the listener's memory, is heard as musical. In this piece each instrument has its own cyclic phrase. The bass repeats the same 1 bar phrase continuously, while the marimba and drums lay down a 4 bar back-beat. The guitar uses a phrase 3 bars in length which means that all the instruments only coincide every 12 bars. After the first twelve bars a lead guitar comes in over the top with an 'improvised' solo, which has no constraints to enforce repeating phrases.

We noticed that if the lead guitar was allowed to start immediately from the first bar, it was very difficult to hear the musical nature of the repeating 12 bar cycle because of its complexity. By having the lead guitar only come in after the twelfth bar the musical cycle can become established in the listeners mind and the music is heard entirely differently - as a back-beat with a lead solo over the top - rather than a complex jumble of notes.

This was also the first piece we imported into Apple Logic to produce a roughly mixed MP3. We probably didn't choose the right instrument sound for the lead guitar, but the end results were so much better than we had heard before from Opus+, some of us were literally dancing around the studio!

The Band Practice

Bars 43 to 80 of 'The Band Practice' was 'composed' while I was in Geneva waiting for a pizzeria to open. I used Opus+ to generate the music, changed the original trumpet part to that of guitar to more naturally accommodate the chords that had been created, (I had the constraints set incorrectly) and dropped the original bass line by one octave (again because I had the octavation constraint incorrectly specified). Then a few days later another piece appeared during a program test run with a very similar 'feel', and the phrase in bar 15 offered a really easy way to link these pieces together. The end result reminds me of a latin band warming up in a practice studio and at about bar 23 they suddenly get 'in the zone' ...

Maximum Funk

'Maximum Funk' is artificially generated! One has to keep this in mind listening to it. There is actual 'structure' here. A slow intro with marimba and guitar that builds, gradually introducing the other instruments and building the listeners expectation, leading to the drums which come in at the start of bar thirteen with a cymbal crash and then they stay under-pinning the whole piece as it builds to a climax. It then changes to 5/4, rather too abruptly, and continues in a hard funk style to the end - which is also somewhat 'interrupted'.

Also included is an orchestral composition by Clive which is based on the original piece generated by Opus+. The lineage is clearly recognizable; there are two distinct sections, the second being noticeably dark and brooding, but the reworking is truly creative and reveals the potential sketched out by Opus+. This demonstrates perfectly how a talented composer can use Opus+ as a starting point for compositions which are unlikely to be considered otherwise. This is Opus+ as an inspirational tool!


'Harmony' is a short piece of 10 bars duration in 5/4 generated as part of a test suite where fragments of music are transformed and located on the staves according to a complex compositional constraints. It has a lovely rolling rhythm and a definite sense of tuneful progression. This is probably the first music that Opus+ produced that sound like part of a human composition as a block. In fact it is reminiscent of some hard underground funk from the 1980's.

Minimum Funky

'Minimum Funky' was the result of a test run on a set of compositional constraints which locate multiple fragments of music across a set of staves and through time - a sort of interleaved continuo. These fragments themselves were generated entirely at random and are included here mainly because of the guitar part; it is the epitome of 70's funk at it's very best.

Jazz Trio

'Jazz Trio' is an entirely unconstrained linear run which in many ways is a 'step backwards' in terms of the way that Opus+ operates, but is included here because it was the first actual music generated after some ten months of work re-factoring the code and radically simplifying the design of the Opus+ library internals to make the entire code base easier to understand and use. Six months of was 'wasted' experimenting with Java template code, which proved to be unsuitable for Opus+ in this context. So this generation of Jazz Trio was a sure sign that we could get back to creative coding, and with the hope that this would proceed more rapidly here on in.

Christmas Collage

'Christmas Collage' works with fragments of well known hymns and their inversions, combining them using pseudo-random mathematics. This is probably the most musical piece so far produced by Opus+, and its an interesting exercise to try and recognize which hymns have been used. Happy Christmas from everyone at Opus+!!!

From Here to Ju-Ju

'From Here to Ju-Ju' is another piece generated from random musical fragments, transformed and combined in unusual ways, but this time there is a distinctive emergent Ju-Ju musical flavour, with alternating bass and answering phrases. Admittedly this style never really establishes itself as it continually collapses into a more chaotic and discordant bastardization thereof, but this is interesting in itself because it's hard to conceive of anyone actually writing something like this.

Rock n'Roll

The main purpose of this 'Rock n'Roll' experiment was to test how different weightings could influence different parts of the composition independently. For example, here the weightings used for the drums greatly simplify the drum parts produced when compared to unrestrained 'jazz' style compositions, yet the guitar part creation is constrained by a different set of weights, which is biased towards small, quick notes creating a contrasting musical effect.


This piece is called 'Rest' because it arose from a test for a routine that analyses musical rest layout. The mathematics underpinning all decisions made during 'composition' are based on a series of integers produced using fractal mathematics; the same sequence that inspired the Mandelbrot set. There are several interesting aspects to this piece. Firstly, it sounds musical. There is a strong sense of a minor key throughout. Secondly, there is an 'invisible pulse' that is subtly apparent through the entire piece. This is stronger in some sections than in others. This is interesting because in nearly all music, the pulse is explicitly stated, whereas here it is implied by an 'emergent conspiracy between the individual instruments'. Thirdly, repeating themes appear with slight variations, which is perhaps unsurprising considering the use of fractals, but at some points the instruments really sound as if they are responding to each other, particularly where some instruments pause for a few bars and the music seems to almost stop only to continue in a quite unexpected way. Fourthly, the piece would be fiendishly complex to perform, and as such is unlikely to be composed by a human, although it could conceivably occur as an improvisation. Lastly, it actually sounds restful. This subjective experience is invoked by the performance of artificially composed music!

Jazz Invention III

This piece, called 'Jazz Invention III' (ooo-er missus!), was generated during a test on 'tonal centres'. Every four bars it cycles between the scales of A minor, C major and the chromatic scale. All decisions regarding pitch, duration and other musical features were taken based on the mathematics of the Fibonacci series, and because the lower bits of the numbers in this series repeat every sixty terms or so, repetitive patterns emerge.


Scales is the first ever 'sound' generated by Opus+, where it proves it can generate all the standard musical scales accurately. Checking that your scales are perfect is just as important for programs as it is for musicians, because we want to ensure that all composition algorithms are translated faithfully to the correct pitches.