I GOT (ALGO)RHYTHM

Dick Pountain/Idealog 258/06 January 2016 14:02

Regular readers might have gathered by now that music ranks equal first - alongside photography and programming - among my favourite recreations. In fact I combine all three in various ways, for example by applying filters to process my pictures, and by writing code to generate musical compositions. It's the latter that concerns me in this column. Around 14 years ago I first became interested in computer composition, and was inspired to write my own MIDI interface in Turbo Pascal v4 (my language squeeze of the time).

Rather than generating real-time music, this unit let me output MIDI files from Pascal programs, which could then be played in my sequencer of choice. I messed around for a while trying to do US-style minimalism (think Adams, Glass, Reich, Riley) constructing complex fugues and phase-change tunes that no human could play. The results never really satisfied me, partly because General MIDI instruments sounded pretty crap through the sound-cards of that era, and because I regularly ran up against shortage of memory problems, using what remained a more or less 16-bit development system. I put the project aside for around 10 years until another spurt of enthusiasm arrived (still using Turbo, but now running in a DOS box on a Pentium/Windows XP system). That time around I made some tunes that were sufficiently convincing to put up on SoundCloud, but there were still nagging problems.

Basically the structure of compiled Pascal confined me to writing quite short tunes. Using fixed length strings and arrays as my main data structures made long-range structure, like successive movements on a varying theme, just too cumbersome to achieve, but creating separate short movements and splicing them together by hand was cheating. My whole intention was to write single programs that generated pieces of recognizable music, interesting if not necessarily pleasant.

Around this time I finally shucked off my (increasingly anachronistic) addiction to Turbo Pascal and fell wildly for Ruby, as documented in previous columns, but never did quite get around to rewriting my composing system in it. There things rested again, until as described a couple of columns ago I remade acquaintance with the hitherto spurned Python language. In order to get up to speed in it I rewrote my venerable Poker program - first effort in Basic on Commodore Pet circa 1980; next in Delphi under Windows; last in Ruby circa 2002 - which translated with surprising ease into Python. Brimming with confidence I thought, it's now or never, and got stuck into rewriting my music system.

I struggled at first because the kind of bare-metal-bit-twiddling (curse you MIDI Variable-Length Quantity!) that's so easy in Turbo Pascal is far from obvious using Python's arbitrary-precision integers. Scanning the forums I soon found a GNU-licensed library by Mark Conway Wirt that does exactly what my old TP one did though, and I was away. Writing the higher level parts proved a revelation. Python's powerful dynamic sequence types the tuple, the list and the dictionary, enabled me to do away with fixed-length arrays and memory allocation altogether, and let me completely redesign the system.

The raw materials of my music remain strings representing sequences of pitch, time, duration and volume values, but now my top-level primitive called MIDIseq.phrase sucks in four such strings, like a ribosome chewing RNA, and chops them up into 4-tuples which are far more efficient and flexible for further processing. All of a sudden, thanks merely to a different set of data structures, my long-range structure problems went away: both horizontal (melody) and vertical (harmony) structures are now essentially without limit. I can write functions to generate random strings, reverse them, invert them, mix and combine them, even evolve them. Python's lambda functions let me generate novel musical scales and apply them on the fly, while iterators offer a fabulously compact way to encode long stretches of melody.

I could hardly be more impressed by this text-book example of what the more savvy computer scientists have been telling us for decades, namely that programs equal algorithms plus data structures, not just algorithms. This deep truth is in serious danger of being lost nowadays, partly thanks to some of the truly awful languages the market has foisted upon us, and partly due to the TED generation's rather naive awe about algorithms. In popular journalism algorithms are all we ever hear about: Google's new search algorithm, the latest AI algorithms, what's the algorithm for a conscious robot, and worse inanities. What neuroscience actually teaches us about the way the brain works is that it's hardly an algorithmic engine at all, and depends rather little on sequential processing. It's really more like a big, soft, fatty mass of fabulously clever data structures. But enough of that, back to my "Contracerto in Z Flat Minor"...

[Dick Pountain is sorely tempted to enter an Internet Of Things fridge for the 2016 Eurovision Song Contest]