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Audio Fast AF1 De-Composer

Atari ST Software

This ST music analysis program was designed for educational use, but it also has the power to compose music to order. Tim Goodyer discovers one of pop's best-kept secrets.

Applying MIDI to music analysis and composition sounds like a tall order, but that's precisely what De-Composer does - and with astounding results.

IT'S DIFFICULT TO entertain the idea of Dave Smith being a "revolutionary" - the ex-Sequential founder, currently Korg R&D boffin Dave Smith, that is. Yet when he conceived MIDI, he began a revolution as significant in its own way as anything Che Guevara might have started. Whatever hopes he may have had for a "universal musical instrument interface", he's unlikely to have thought about it as a tool to help analyse and teach classical music composition - yet that's just what Audio Fast have set out to do with it in their AF1 De-Composer program for the Atari ST.

De-Composer is designed to store and analyse music entered into it via MIDI. That is, it will assess incoming MIDI data for its musical content and present you with the sort of analysis commonly taught using conventional classical instrumentation, records and manuscript paper. On top of this, it will allow you to impose the compositional style of one piece of music on to another, or even generate new pieces of music in a particular style.

The documentation tells us that the program has been written specifically to cope with the music taught in British higher education, but obviously any music presented to it as MIDI data can be subjected to the same processes. As such it is being marketed as educational software, but the ramifications of this program are somewhat more significant, as we shall see later.


DE-COMPOSER RUNS ON any ST from a 520 upwards, with restrictions being placed on the amount of music it is able to handle accordingly. The program comes on a single disk and is software copy-protected - so there's no dongle to lose.

Operation is from two main screens, the Decompose screen and the Compose screen. Different aspects of the musical analysis are presented on a number of dedicated screens (key signature, time signature and so on). All the De-Compose screens can be printed out, but there is no provision for printing music on a stave. Decomposer makes no claims to be a scorewriter for under £100.

Using the program is as simple as connecting a MIDI controller (presumed throughout the manual to be a keyboard) to the ST's MIDI In (connection to the MIDI Out is obviously required for composition), setting the time signature and start tempo, clicking on the Initiate Button and putting fingertips to ivories. De-Composer gives you a one-bar count and you're away. And it's here you'll notice the first impressive feature of the program, because the metronome bleep (from the Atari's internal speaker) fades out after the first bar, leaving you free to alter your playing speed at will. The program performs its first analysis on the "Style" of the first bar and uses this information to recognise how the tempo of the music changes during your performance.

You can repeat this process to add up to two further parts - allowing you to build up a reasonably complex piece of music. In this way you can selectively enter parts of an orchestral score to see what makes them tick.

Once you've finished playing, a click on the Terminate Button automatically initiates the Decompose routine. Now, this process can take as little as a couple of seconds or as much as several minutes depending on the complexity of the music. Once the analysis is complete, however, you are free to examine the intricacies of the music you've just played.

Specifically, the analysis covers the obvious time and key signatures, including any changes that might occur during the piece, and extends to the more academic aspects of melodic curves and harmonic structures, as well as delving into the overall structure of the music.

One of the strengths of a software-based system like this is that it is able to assemble the data in a number of different ways to suit your requirements. The main presentation takes the form of a list of observations plotted against bar number. This vaguely resembles the event lists of conventional sequencers - the bars are listed in sequence in a vertical column and against them appear details of the music. Alternatively you can ask De-Composer to give you the bar numbers of any changes in time signature, for example.

The melodic curve takes the form of a graph of the melody (with reference to either a user-defined or computer-derived reference note). The harmonic analyses appear on the same graph and are presented as a number of further curves (dependent upon the number of harmony lines) all plotted with respect to the same reference note. When run in colour, De-Composer allows you to assign different colours to make these curves more distinct. Finally the overall musical structure appears as a listing of the development of the piece as it progresses through time. Here you may be presented with anything as simple as verse/chorus structures or as involved as sonata form, such is De-Composer's versatility.

"Thanks to De-Composer anyone can now 'write' a No. 1 hit with absolute certainty - whether you personally find this a satisfactory state of affairs is another matter."

All the above information is available as printout in any of the screen display formats.


THE WAY IN which De-Composer goes about both analysing and creating music is by creating a musical algorithm - called a Style algorithm. Being essentially mathematical in construction, it's possible to create an algorithm - or set of rules - which describes the music in a mathematical form. The same principle is employed in "intelligent" composition programs like Hybrid Arts' Ludwig, but such programs are designed to produce music from scratch while giving you control over various aspects of the composition.

A Style algorithm contains all the information necessary to describe the piece of music from which it was derived - this was more or less confirmed by asking it to compose new pieces of music based purely on the Style algorithm of pieces it had just analysed. Without any additional instruction, De-Composer should, in theory, "re-compose" the piece it has just "de-composed". While there were discrepancies between the "new" pieces and the originals, all were recognisable as the original pieces, and simpler pieces were almost perfect "re-compositions".

Reconstructing existing pieces of music is not what the program was intended to do, however. Instead, by entering the Input page, you can amend existing parameters or add fresh parameters to the Style algorithm. Using this modified algorithm, you can generate variations on an original piece. Further, you can take the algorithms derived from up to ten pieces of music and combine them to produce a new piece that draws on all ten, yet is distinctly different from each one.

Again the intention of the program's authors is for you to be able to compare what you believe a composer might have done with a piece of music with what algorithms of his music suggest he would have done. What they have not fully realised, however, is that the program is in many ways more suited to dealing with contemporary music than classical music.


REMAINING WITH THE intended application of De-Composer for the time being, it's good to see that the program is MIDI Song File compatible. This means that you can draw on the resources of companies like Digital Music Archives who specialise in producing classical music in MIDI sequencer format. This can save you considerable effort in "keying in" the work you wish to study. Of course it also means that you can prepare pieces on other sequencers (as long as they too are MIDI File compatible) and then load them into Decomposer. It also means that you can offer your own work up to De-Composer for analysis...

All this is interesting and potentially useful stuff, but things start to warm up when you stray away from the "serious" educational applications of Decomposer. After working with the program for a short period of time, it became apparent that what I had in front of me had the potential not only to analyse pop music and tell me what, say, the last ten No. 1 singles had in common, but to compose music in a similar vein. Broaching the subject with Audio Fast, the program's originators, elicited what can only be described as a feeble attempt to fudge the whole issue. Discussing the same issue with one of the program's beta testers told me why. It seems that early copies of De-Composer were first circulated almost five years ago and one fell into the hands of a pop production partnership. He wouldn't disclose to me who the producers were, but assured me that they had since cornered the market in production-line pop hits. All they had to do was take a handful of tunes currently favoured by the record-buying public, feed them to De-Composer and then ask the program to compose another handful with similar appeal. The suggestion was that the process was so successful, they're still doing it today.


AS AN EDUCATIONAL aid, De-Composer is an ambitious project which succeeds in its chosen purpose exceptionally well. It suffers from one main drawback, however, and that is its reliance on your ability to play into it what you want analysed. Happily, its MIDI File compatibility should help out here. But it's as a means of producing pop music to a successful formula that the program really shines. Thanks to De-Composer anyone can now "write" a No. 1 hit with absolute certainty. Although whether you personally find this a satisfactory state of affairs is another matter.

As it was intended to deal with the complexities of classical music, De-Composer has no difficulty in unravelling most popular music - the exceptions being sample-based pieces, where the sample source is at least as important as its sound. The skill in applying such a program to chart music comes in your choice of songs to analyse, and the elements of those songs you choose to favour or suppress.

In spite of Audio Fast's reluctance to associate their program with pop music I don't really see how they can hope to prevent it. I suspect that a new era of compositional "talents" is upon us, and with it a new generation of arguments about "real" music and "real" musicians.

Price £99.95 including VAT

Audio Fast are presently arranging distribution of De-Composer; any enquiries, by post only, to Audio Fast, (Contact Details).

Previous Article in this issue

On The Beat

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Dream Factory

Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Apr 1991

Review by Tim Goodyer

Previous article in this issue:

> On The Beat

Next article in this issue:

> Dream Factory

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