Acorn Music 500
Synthesiser Hardware and Software for the BBC Micro
Acorn's first venture into music synthesis boasts some good-looking synthesis hardware and a music composition language - AMPLE - that grows with the user. David Ellis has the advance details.
An exclusive review of a new British-built computer music add-on that incorporates a programming language designed specifically for musicians.
Ah well, Christmas is coming, the geese are getting fat, and people are thinking of pressies - a ripe time for the launch of Acorn's latest box of merriment. But no, this isn't the Model C BBC Micro, or indeed anything to do with their growing interest in business computing. Instead, in all but name, the Music 500 is a second processor specifically designed for high quality sound synthesis, but inclusive of some special software by the name of 'AMPLE' (standing for Advanced Music Programming LanguagE). And as I hope this review will show, it is remarkably advanced, knocking spots off all previous attempts at giving musicians their own programming language, and for an astonishing all-inclusive price of £199.
Well, there are two sides to the story - the hardware and the software - and both start with another Cambridge company by the name of Hybrid Technology. We first reported on their endeavours in Rumblings back in E&MM October 83, when the story went something like this: 'Well on the way are a couple of really smooth British (about time too...) programmable digital sound generators for home micros. Specs are elusive at present, but one would appear to have 12 channels each with a 64kHz sampling rate and offering all sorts of yummy modulation options, whilst the other goes for more channels (32) with a lower sampling rate of 32kHz. The former is expected to appear initially for the BBC Micro, and not surprisingly, Acorn are showing a lot of interest. With expected price tags of under £200, these look like just what the doctor ordered...'
A year later, the pudding turns out to have proved itself in no small way, though the hardware almost undersells itself in its disk drive-sized case (actually, it is a disk drive case) that plugs into the BBC Micro's 1 MHz bus and produces a stereo output via a five-pin DIN socket. The Music 500 synthesiser box also includes its own power supply, so there's no question of over-stretching the Beeb's resources.
The design of the hardware mirrors the 'time-sharing' principle of both the alphaSyntauri's five-year-old synthesis hardware and the Clef Products system featured until last month in the E&MM Digital Music series, the second system referred to in the above quote. But Hybrid Technology's design goes much further. Gone are the days of annoying aliasings and restricted bandwidths, because with an individual channel sampling rate of 46.875kHz (a couple of kHz faster than the Compact Disc, in fact), there's quite simply more harmonic space to play around with. Add to that some ingenious design concepts like 'oscillator indexing' at a rate of six every microsecond, which permits all manner of powerful modulation tricks like FM, ring modulation, pseudo-random noise, and synchronisation, and you begin to get a taste of the thought that has gone into the hardware. Then, for the icing on the cake, there's the logarithmic coding of wavetables, which allows digital multiplication to be achieved simply by adding logs together (remember school days?), thereby getting around the breakfast cereal crackles and pops present in other systems. And with a complementary multiplying DAC, this gives a dynamic range typical of the best companded eight-bit systems.
Where Music 500 really stands or falls is by the software that runs the synthesiser. The basic aim behind this was to create a programming environment that would grow from the base up to result in a powerful, integrated system. Indeed, the intention has now been extended even further in the direction of a standardised language for producing music on different micros. Grand ideas, to be sure, so AMPLE has got a lot to live up to.
But let's start by seeing where AMPLE and the Music 500 synthesiser fit into the standard BBC Micro picture (Table 1). In essence, the Music 500 system works in a similar manner to the BBC Micro, where running a program directs the Operating System's queue control to send bytes in an orderly manner to the humble sound chip. But even given BBC BASIC's callable PROCedures, and their strong similarities to the organisation of musical material, BASIC is a poor language for musical activities. The point is that music is all about simultaneous events rather than events carried out in turn, which is where AMPLE really comes into its own. Indeed, if there's one principle that sums up AMPLE, it's 'concurrency' - meaning doing a number of things at the same time - and you can bet your bottom dollar that it'll be this that earns musical computers their slice of the bread in years to come.
One of the intriguing things about AMPLE is that features that users can easily write for themselves aren't provided as standard. Instead, the features that are already present are there to allow you to build other features. If this sounds like a tautological conundrum, take the building industry as a comparison. Bricks, mortar, wood, and cement are provided as standard, but if you want to build a Taj Mahal in your back garden, it's up to you to draw up the plans and construct your own suburban folly.
Starting at the system's most basic level, there are the note words illustrated in Table 2. Then, applying some duration values to the last-mentioned, and giving the whole thing a name and an instrument to play it, we get the contents of Table 3. At this juncture, we've already experienced a number of important things about AMPLE. Namely that a) notes are specified in both cases - upper case to go up and lower case to go down, b) note durations are of values commonplace with 48 pulses-per-quarter-note drum machines, and c) the language works on the principle of 'words' for labelling music ('GstQ'), instruments ('HM's tpt'), instructions, or whatever and wherever your creative urge takes you. The reasoning behind the use of combined-case notes goes something as follows:
1 Music is essentially linear - it goes up and down and moves to the right.
2 The printed score shows this by the direction of lines joining groups of notes, but doesn't make any visual distinction about octave break-points, unlike MCLs running on systems as diverse as the Fairlight and a Spectrum MIDI sequencer.
3 When home computers were only capable of upper-case display, notes could only be shown in upper case, yet the practice has lingered until the present day.
4 AMPLE attempts to mimic this visual linearity of music by using both upper and lower case note words. At the same time, this reduces the number of key entries required to enter such tricky things (for MCLs) as trills (especially between B and C!), scales, and octave shifts.
But it's the 'word' side of AMPLE that's the most important to take home from this review. Like the languages FORTH and LOGO, with which AMPLE has a lot in common, Hybrid's brainchild works using a stack of words (50 in all) that can be defined by the user for whatever purpose he has in mind. Thus, in the case of the Pachelbel example (Table 4), you'll find a couple of words used to define the two parts, a word for instructing the ARTS as to how the piece is to be conducted (key signature, tempo, and the number of beats in the bar), a further word to get all the parts and instruments orientated in time and space, and finally the words used to define the actual instruments. But you could just as well define a couple of words to produce major and minor arpeggios, a word to set a transposition action, and then a further word to gel the whole lot together into a playable entity, as in Table 5.
What all this tells us is that AMPLE is a Music Composition Language - no, a Music Production Language - that grows with you. If your only interest is the straightforward rendition of Bach with pseudo-authentic Baroque instruments, then fine. That's easily accomplished. And you've a choice of entering it using either the text buffer to store lines of music, or for more complex pieces, a word processor like VIEW to assemble the text, which can then be *EXECed into AMPLE. But AMPLE goes a great deal further than the plain coding of music and its synthesis. Because AMPLE is a true programming language, with a host of programming words for performing operations on numbers and strings, control structures, and input/output, it's ideal for extending the user's horizons into the realms of algorithmic and chance procedure composition. Take a line like the one in Table 6, for instance. Transpose it up and down a few octaves, do a few permutations of the notes, assign it to a number of contrasting percussive instruments, add a high C eighth-note pulse, and you've got a realisation of Terry Riley's 'In C' that will never sound exactly the same, simply by virtue of AMPLE's RAND word.
And that's just the tip of the iceberg.
AMPLE nominally configures the system's 16 output channels into eight pairs. However, you're entirely free to reconfigure them, if that's what you wish. But the real beauty of the system lies in the way in which multiple-waveform voices can be set up with all manner of inversions, offsets, sync, timbral variations, and stereo field spreads, in fact, once you've experienced the mind-blowing chorusing, phasing, and sync sweep that ensues, you realise that the Music 500 is one system where asking for separate output channels is somehow missing the point...
When it comes to envelopes for pitch and amplitude modulation, users have the option of either using files of presets supplied with the system or constructing their own. The latter takes a good deal of effort, as shown by the example in Table 7 for playing alternating fifths with a slide in between.
Still, surely it's better to have that sort of flexibility than not at all? And if you get stuck, you can take heart in the fact that the excellent manual and reference section provides plenty of examples. Not surprisingly, the definition of waveforms can be similarly complicated if you choose to use all 16 of the permitted harmonics. On the other hand, you can also elect to fill a waveform simply by using that rather useful RAND word (Table 8). And if you want authentic-sounding percussion with built-in ambience, try this Simmons lookalike sound (Table 9) that makes excellent use of ring modulation.
Hybrid Technology are currently working on a four-octave keyboard that has its own processor and will plug into the BBC Micro's 1MHz bus. AMPLE will then support the use of the keyboard both as a conventional real-time input device and as a scoring device for creating musical 'words'. On top of that, you'll also be able to define your own highly-specialised keyboard instruments that will insert into the data stream from keyboard to synthesiser box.
Of particular importance when it comes to the acceptance of Music 500 by more studio-minded musicians is the news that Hybrid are working on a simple time-code system that'll enable the BBC Micro to send and receive sync data when connected up to a multitrack. There are various technical problems to be sorted out first, but the system has a headstart in using a time-base that's identical to that of the LinnDrum et al (48 pulses-per-quarter-note) and is therefore an ideal sync source.
MIDI has also entered into Hybrid Technology's thought stream, but they're reluctant to make any positive moves in its direction until 'MIDI comes of age', as they put it. However, the point about the system's modular design is that adding on MIDI is actually very straightforward (it's really just a question of replacing ARTS - the software extension of the synthesiser - with whatever's needed for interfacing Music 500 with the MIDI).
One of the other intriguing developments Hybrid have come up with for their own internal use is a pitch input box that allows the Music 500 system to be controlled from any pitch source - keyboard, voice, or otherwise - by the simple expedient of plugging in a microphone. Initial teething troubles with harmonically complex sources (my voice, for instance!) seem to have all but vanished, and although Hybrid have no immediate plans to market the thing, there's no doubt that a similar facility will be figuring in their future plans.
Acorn must have a winner here. The price is right, the quality of sound is simply superb, and AMPLE is the bee's knees.
If there's any criticism to be made, it's that getting the best out of the system takes time, and that's especially true when it comes to constructing genuinely new and interesting instruments using the various modulation and envelope options. But like buildings, complex sonic edifices aren't manufactured overnight, so a measure of exploration and experimentation is inevitable. Anyhow, any problems in that direction are overshadowed by the fact that AMPLE offers musicians (at long last) the opportunity to program in a language that's designed for them rather than head-bangers, hackers, and the like. And the fact that a music keyboard isn't involved at present may in fact be a blessing in disguise, in that it should encourage users to get the most out of a system that makes a virtue out of positively encouraging continually changing creative directions.
In short, I'm hooked by it.
Further information: Hybrid Technology, (Contact Details).
Review by David Ellis
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