Yet more British innovation, this time in the form of a MIDI-equipped sampling system for the world's most popular home micro. It's remarkable value for money.

If you're a reasonably long-standing E&MM reader, you'll probably remember a review of the Microsound CBM64 keyboard and sequencing software appearing in the July '84 issue. A postscript to that review drew attention to the fact that a sound-sampling add-on had been fully developed. Well, that unit - complete with software - did put in an appearance towards the end of last year, but it has since been completely upgraded (it's now MIDI compatible and offers a longer sample time, among other things) and given a stylish casing.

And it's this new improved version, now being marketed under the rather grand title of Digital Music System and scheduled for general release in June, that's the subject of this review.

Overview

The Digital Music System (henceforth referred to as DMS, you'll be glad to know) is a monophonic sampling system with a maximum 33kHz sample rate. Minimum sample time is one second, with the sample and all user-defined variables being held in 40K of the Commodore 64's memory. Looping of samples is one of the facilities supported, with the system's editing facilities being capable of eliminating just about any inherent glitches you might come across. And once it's been edited to your satisfaction, your sample is playable from Microsound's own music keyboard, any MIDI keyboard, or the 64's QWERTY keyboard - a handy range of controlling options.

The sampling unit itself is a slimline 9" x 5" cream and black affair that connects to the Commodore via the cartridge port, and requires either PP3 or PP6 batteries or a 9V DC power supply in order to function. Included in the unit are a programmable 24dB antialiasing lowpass filter to reduce distortion (and with cutoff variable between 4kHz and 15kHz), and pre/de-emphasis circuits to reduce quantisation noise. All very sensible so far.

The unit's front panel houses a quarter-inch jack socket for mic/line input and rotary knobs for adjusting input and output levels, the latter also functioning as an on/off switch. The back panel contains a jack output, 9V DC input, and MIDI In and Out sockets (standard-issue five-pin DINs), as well as sprouting the ribbon cable connector to the 64.

And at the other end of the ribbon cable we find... an Issue One DMS Interface card, which in turn slots into the 64's cartridge port. The card on the review model was left bare to the world, a state of affairs that I hope will be rectified on the production models.

Sampling Time

Depending on which keyboard option you decide to go for, one of three control programs has to be loaded, a process that's clearly detailed in the user manual. Complete loading of the control program (whichever one you opt for) takes place in three stages, with an overall loading time of under a minute - refreshingly brief, that.

With the loading complete, the program's main menu confronts you with five options: Sample, Control Functions, Play, Edit, and Disk Options. Being a fairly logical sort of bloke, I started with the first of these.

Now, one of the biggest headaches of trying to get a decent sound sample is deciding precisely when to begin recording. As a rule, there are simply too many parameters to consider in too short a space of time for the human brain to cope. However, Microsound have given their Sample page two controls aimed at easing just this problem. First, there's a trigger delay facility that allows you to set a countdown of up to 255(!) seconds, then, once your countdown has reached zero, the trigger level parameter comes into the picture. What this means is that the sampling process isn't activated until the input signal reaches a predetermined level, this being implemented on a scale of 0-127.

As for the sample rate itself, this may be set at anything from 4-33kHz, giving a maximum bandwidth of 16.5kHz - certainly a reasonable figure. Anti-aliasing filter amount is selectable on a scale of 0-255, which is all very well, but what a shame you can't select the cutoff frequency itself. As things stand, selecting a suitable filter amount is a decidedly hit-and-miss affair, and you'll never derive the full benefits obtained from knowing what's really going on.

Anyway, once the above parameters have been set, you're given the opportunity to set a suitable master input level against your chosen trigger level, with a fluctuating 'bar graph' giving appropriate visual feedback on the monitor screen.

This done, the countdown begins onscreen, and assuming you've selected a non-zero trigger level, the system pauses at zero until a suitable signal is registered, at which point the screen goes blank to indicate that sampling is taking place.

All very straightforward. One small gripe, though. There's no Escape option provided, so if you select the Sample page by mistake, it's bye-bye to any sample already in memory.

Sample Editing

Recording a sample is only part of the story, however. The DMS offers a number of editing options based around a time-domain waveform display of the sample, and a flexible pointer system that allows sections of the waveform to be manipulated quickly and easily. Not quite yer actual Fairlight, you understand, but useful nonetheless.

The Edit page uses a hires/text split screen to display the sampled waveform, together with information on the various editing options available. The waveform takes between five and ten seconds to draw on the screen, depending on its complexity. What's particularly neat is the way Microsound have limited the display to a single screen (and kept to a workable resolution), which means you can view the waveform in one go without having to worry about scrolling screens and the like.

The basis of the DMS' editing system is the pointer set. There are two of these, each of which can be used to define any area of the sample storage memory. They have a dual function in that they also define an area to be sampled into - a clever bit of design that increases the power of the system (though inevitably at the expense of sampling resolution) by enabling several different samples to be resident in memory at once.

The two pointer sets are selected by pressing f1 or f3 on the Commodore's QWERTY. A crosshair is moved along the horizontal axis of the display by using the cursor keys, and start and finish points are selected by pressing 'S' or 'F'.

Currently-assigned start and finish points are indicated by further crosshairs, but although these are colour-coded for clarity's sake, this actually reduces visibility if you don't have the requisite colour TV or monitor, which is a bit silly.

"The sampler's response time is good enough to handle the fastest runs on both MIDI and Microsound keyboards."

The pointer sets are themselves part of the edit process, but once you've defined a particular area of memory/segment of waveform, there are four editing options that enable you to do ghastly things to your lovely sample (or vice versa, as the case may be). These are Mix, Gain, Reverse and Delete.

The pointer sets can of course be redefined at any time without there being any effect on the actual contents of memory. Mix, Gain and Delete, on the other hand, have an irreversible effect on the selected area of the sample, though Reverse is potentially non-destructive by virtue of the fact that anything reversed twice reverts to its original form. Or at least, that's what I think James Burke was saying the other night.

Space considerations prevent me from going into detail on the editing facilities, but in common with so much of the Microsound system, they're well considered and easy to use. The Gain option simply increases the amplitude of the portion of sample determined by the position of the pointer sets; Mix merges two such determinable segments together and places the result in the second of the areas; and Delete simply removes the delineated segment of sample and automatically closes the gap it occupied previously. The pointer set system, incidentally, succeeds in being both enormously flexible and splendidly successful at the same time.

Performance Stance

So, you've now got the sampled sound of your dreams locked safely away in the Commodore 64's memory. All you need now is some means of unleashing it onto the unsuspecting musical world. And as I've already hinted, Microsound have covered just about every eventuality in this department. If you don't own a MIDI keyboard and don't wish to incur the inevitable expense, you can opt for Microsound's own four-octave keyboard, which connects to the 64's two joystick ports and will set you back a modest £149. It's a perfectly usable keyboard, if a bit on the spongey side.

As an even cheaper alternative, you can 'play' the 64's QWERTY keyboard over four octaves (one octave plus switchable transposition). It's not ideal, but it's nice to know the option is there if you can only afford the sampler unit and software for the time being.

As for MIDI implementation, this covers basic note on/off reception, but importantly, the receive/transmit channels can be set to any one of the standard MIDI 16. This worked perfectly with a Casio CZ5000, and raised all sorts of sonic possibilities in the process. Only hiccup was that pitch became unpredictable when the keyboard was played outside of the Microsound's four-octave range - the CZ5000 has a five-octave span. My fault for trying to be too clever, probably.

On a brighter note, and of far greater significance, is the fact that the sampler's response time is good enough to handle even the fastest of runs on both MIDI and Microsound keyboards.

And so to the Control Functions page. This controls various performance features, most notable of which is a split-keyboard facility that splits the four-octave keyboard in half and places Pointer Set 1 on the left and Pointer Set 2 on the right. Don't get too excited - the sampler is still monophonic. But the facility does enable two sounds to be placed on the keyboard at the same time, which can't be bad, and it works equally well with either MIDI or Microsound keyboards.

But there's no point being able to do all this if you've got no means of storing your endeavours for posterity. As I've said, the sample and all user-defined variables are stored in 40K of the CBM64's memory, and this 40K can be saved to disk for later (though probably not 'instant') recall. Option 5 on the main menu controls loading and saving of samples, as well as cataloguing your sample disk from within the program, and the deletion of samples. You should find it possible to cram a maximum of four samples onto a single floppy, which is a lot better than some systems manage.

Conclusions

Any sound-sampling system ultimately stands or falls on the quality of its sampling, no matter how many additional facilities it offers. Happily, the Microsound DMS performs very well in this respect - and not just at its maximum sample rate, either.

The system succeeds in acting as an introduction to sampling, but more than that, it's good enough for use in semi-professional studio environment - so long as you're not bothered by the time it takes to save and load samples to and from disk.

And there's plenty new cooking in the Microsound kitchen, like an EPROM containing the complete DMS software for instant access on power-up, and a plug-in RAM card holding about five samples for instant access and switching. That should help quicken things up a bit.

Moving back to the present, the DMS control software is generally well conceived and easy to use, and provides enough in the way of editing and control facilities to provide a flexible system that's really musical in its range of application. The accompanying manual is clear and concise, too - no excessive verbiage to wade through here.

The time taken to add MIDI has been time well spent, and its inclusion opens up the possibility of the sampler being incorporated into a MIDI sequencer-based setup, something lack of time prevented me from doing during the review period, alas.

Asked whether or not I'd buy a DMS if I had the money, my initial reaction was an uncertain one. Then I tried to think of possible competition, and realised there wasn't very much. If you've already got a Commodore 64 and disk drive, you'll regret not taking the DMS for a test.

Even in these Mirage-infested times, the Microsound stands out as being a winner.

The DMS carries an RRP of £249, while the CBM64 music keyboard is a further £149, both including VAT.

Further details from: Microsound Ltd, (Contact Details).