Action Replay

Lots of movement on the British front this month. Jolly good show, too. First to kick oft is Ricoll Electronics and their 'Action Replay' (Frank Bough, eat your heart out)...

The basic premise of 'Action Replay' is to act as a sound sampling add-on for the 48K Spectrum. In fact, Ricoll have been beavering away in all sorts of directions to further the musicality of the humble Spectrum, and this, their latest offering, should offer the Computer Musician plenty of food for thought. Anyway, specs for this go as follows:

Input sampling rate: up to 32 kHz
Sound storage: 32K
Storage time: 1 to 8 seconds
Overall S/N ratio: -66 dB
Quantisation noise: -72 dB
Distortion: not audible (!)
Filter: -36 dB/octave on input and output
Frequency shift: at least +/-4 octaves
Controls: mix and feedback
Options: vibrato, glide, and CV input

What Action Replay comprises is a single box of tricks (rather than the three of a competitor's product) that connects to the Spectrum's edge connector. By using companding chips for the DAC and ADC, the unit is capable of rather better quality than is customary with the sort of 8-bit sampling techniques used in the Decillionix DX-1 (reviewed in CM a few issues ago) or the other sound-sampling Spectrum add-on just alluded to. With the hardware come various software routines that allow sound to be recorded, played back in straight or reverse modes, looped around selected points for a glitch-tree sustain, harmonised +/-2 octaves, and echoed from 1 to 8 seconds.

Other software modules are also available, and these include Fourier synthesis and analysis, waveform drawing, and real-time spectrum analysis. It's also claimed that the software will be compatible with Microdrives so as to facilitate fast(er) retrieval of sounds. Another interesting addition that'll be following shortly will be a module that allows voltage control of the sample playback frequency from any 1v/octave synth or sequencer. The only pricing detail we have at present is a tentative 'about £99' for the Action Replay hardware and standard software. For more info, contact Eric Bulmer at Ricoll Electronics Ltd., (Contact Details).

Clef Computer Music System

Back in October's 'Rumblings', I mentioned that there were a couple of Programmable Digital Sound Generator add-ons of near-neighbour origin about to appear on the market. Well, it seems that it's the Clef 32-channel, 32 kHz sampling-rate one that's made it first, and what follows are the provisional details of how, why, and what it's all about.

Basically, the PDSG consists of a fast DAC that's time-multiplexed 32 ways, so that, in effect, one ends up with 32 'logical' oscillators, each being fed their own waveform samples from on-board RAM and ROM (up to 8K in toto), as well as control bytes for setting frequency and amplitude. In comparison, the Mountain Computer Music System hardware used by the alphaSyntauri and Soundchaser systems has only 16 oscillators.

These are fed waveform samples from the host's memory via direct-memory access which halves the effective speed of the processor. So, whereas the 6502 in the Apple is forced to run at 500 kHz when the MusicSystem is in operation, the Clef PDSG leaves the 6502A in the BBC Micro running full-speed at 2 MHz, ie. giving four times the computing power, and that, of course, can be used for controlling more parameters in less time.

One of the major complaints levelled at the MusicSystem hardware is the excessive amount of noise coming through when no sound is actually being outputted. To get around this problem with the PDSG, hardware noise suppression has been added so that inactive oscillators are automatically silenced. A further limitation of the MusicSystem lies with its inability to respond fast enough to what's going on around it. The problem lies with the rather slow on-board interrupts generated every 8ms. Since these direct the frequency and amplitude updating of the oscillators, it follows that the earliest a keypress can be turned into sound is 8ms later, and that's with everything working optimally. The long and the short of this is that chords are uneven and percussive attacks fall a long way behind what they're actually meant to be.

Clef's PDSG, on the other hand, is capable of responding with an edge rate of just 2ms if that's what's required by a particularly percussive attack. Another significant improvement over the American system is that all 32 oscillators can be assigned to left, right, and centre positions in a stereo field, whilst the MusicSystem is hardware-fixed to 8 on the left and 8 on the right.

However, to make all those 32 oscillators earn their keep, they've got to be used in an intelligent fashion, which is where Clef's system really scores over those from Syntauri and Passport Designs. The present software allows 1 to 4 oscillators per note (each with different waveforms, ADSRs, frequency offsets, and velocity-dependence), thereby giving a minimum of eight-note polyphony. But because there's no hardware dictation of oscillator grouping, short-lived oscillators can be dynamically re-allocated as needs require - the same principle that's used in the Synergy, in fact.

It seems that the way the PDSG is initially going to be used (in a commercial sense, anyway) is as the basis of a Computer Music System that revolves around the BBC Micro. No doubt that fact will be greeted with roars of delight from all those BBC Micro owners who've got past believing that SOUND and ENVELOPE statements are the passport to instant nirvana... In fact, the 'BBC Micro User' show, held in London at the beginning of December, saw the prototype of Clef's product doing its thing on the Watford Electronics stand under the able digital manipulation of its designer, Alan Boothman. Aside from the hardware that's doing the digital synthesis, the unit that was being earmarked for sale from the end of February will also include a 5-octave keyboard with programmable touch-sensitivity and, as a later option, the luxury of after-touch pressure sensing.

Software is still under development, but what was seen at the London show allowed the setting-up of oscillator parameters, assignment of multiple oscillators to each voice to create interesting timbral changes and/or chorusing and delay effects, programming of touch-sensitivity and keyboard splits, and some fairly basic real-time sequencing.

It would seem that Clef's main aim at the start is to provide an instrument with a good range of imitative sounds that really responds to the performer. In doing so, I suppose the Clef system is going somewhat against the grain of what many micro musicians are after (non-real-time input), but it is following on in the tradition of other eminently playable instruments like the Synergy and Chroma. What has to be remembered is that the Clef system will be selling for a fraction of the price of the above and, most importantly, is designed for interfacing with an extremely popular micro. That must mean that huge amounts of further software - non-real time, educational, you name it - will follow suit. It deserves to do well.

And the price? Well, that hasn't exactly been finalised, but Clef are anticipating 'under £400 for a system', and that's inclusive of software to run it from the BBC Micro, probably the Apple II, and possibly certain other micros. The PDSG itself will in fact be appearing as a project in E&MM in a few issues time, and it's anticipated that it'll sell readymade for around £150, but for more info on the system as a whole, contact Clef Products (Electronics) Ltd. at (Contact Details).

ICMC '84

The International Computer Music Conference is described as 'the premier forum for exchange of the scientific, technical, and artistic aspects of computer music'. The 10th ICMC is being held in Paris from the 19-23 October 1984 at IRCAM and the Centre George Pompidou. The main topics of the conference include the following (quoting from the conference info sheet):

1 Processing and synthesis hardware, including VLSI design strategies.
2 Synthesis and compositional software, including real-time control.
3 Signal-processing, acoustics, and psychoacoustics.
4 Computer-assisted composition, research, and instruction.
5 Affordable systems based on microprocessors.
6 Aesthetic and theoretical implications of computer-based methodologies on composition and performance.

In addition, there'll be a healthy proportion of concerts, including a performance of Boulez's 'Repons' by the Ensemble Contemporain on the first day of the conference, two live concerts each day, and tape playbacks throughout the conference. Interested parties are invited to submit tapes, papers, and pieces for tape and/or live electronics and instruments. In case you're worried about the limitations of your 'O' level French, you'll be glad to hear that simultaneous translations in both French and English will be provided!

Unfortunately, there's a registration fee involved in attending the conference. If you're not a student, this is 600F (around £50); if you are, it comes down to 300F. On top of that, there's accommodation to be considered (prices start at around 275F per night for a single room in a two-star hotel). For more information and/or a registration form, write to Mrs. Danielle Guichard, Via (Contact Details). By the way, registration forms need to be sent in by the end of March, scores and performance tapes before February 1, and papers and tape pieces by May 1. So now's your chance to chat with the luminaries of the computer music world and see whether IRCAM is really all that it's cut out to be! Here's to a strong British presence at ICMC '84...

(Apologies for the jingoistic spirit that's crept in this month, but that's what comes of writing the column on New Year's Eve!)