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Clef Computer Band-Box

If and when the Last Trump comes, there must be a good chance that Clef's Computer Band-Box makes it to The Great Digital Design Centre just out of sheer ingenuity and perseverance against all the odds. Seeing that Clef is a British company, that might sound like nepotism or blowing one's own (country's) trumpet, but, let's face it, synthesiser manufacturers in this country had had a pretty raw deal in the past, judging by the experiences of EMS and Electronic Dream Plant, and they deserve all the help they can get.

As it happens, there is a touch of the 'dream' about the Band-Box, because the frustrations that the designer encountered in playing sax in bands — drunken drummers, keening keyboards, and so on — encouraged him to pursue the goal of 'developing electronic musical instruments which assist the task of the solo musician'.

Put simply, the Band-Box provides a backing trio of drums, bass, and a chord instrument. What makes the unit different to the auto side of the average 'does-all-bar-making-the-morning-tea' electronic organ is that virtually everything is programmable by the user. In fact, the Band-Box is intelligent, in the digital as well as analogue sense of the word (there's a 6502 microprocessor taking charge), and that gives it quite a competitive edge over (thick?) units that might appear superficially similar.

Rhythmic Starts

An extremely unusual feature of the Band-Box is that part of the unit is another Clef product, the Master-Rhythm. In fact, the latter actually fits inside the Band-Box case. For any of the 1,000 or so owners of Master Rhythms this must be good news, because one can convert one's technological backing-track from drums to trio by buying the Band-Box minus the Master Rhythm. It's almost like going from a mini to a sports car by supercharging the old engine and putting the chassis in a new body shell!

Whereas many programmable drum machines of this type have a rather restricted number of voices and rhythm memories, the Master Rhythm has a healthy complement of 12 different voices and 24 memorised patterns of varying lengths. The memory and read/write control is configured rather like an 8-track tape recorder on which recording is carried out one part at a time and playback is from all 8 tracks simultaneously. The recording mode is selected from the Program Control switch, i.e., from bass drum, low tom-tom, high tom-tom, snare, rim shot, long cymbal, short cymbal, or accent options. Each of these tracks can then be fed to one of three groups of instruments according to the position of the Instrumentation switch (see Table 1). The accent track has the effect of overdriving the final output stage of the unit, and this allows a certain amount of dynamic spice to be added to a particular percussive event.

In general, the quality of simulation is pretty good — especially the bass drum, snare, cymbal, claves, and conga. In all honesty, it can't be said that the cymbal sounds like the real thing — all manner of ring modulation tricks are needed to procure a convincing metallic 'zing' — but the unusual noise generation circuit (an op-amp operating at very high gain) and tune filter produces a very fair and listenable sort of sound which is better than the usual filtered white noise. The least convincing sounds were the t-toms, and I think this has something to do with the rather 'overtuned' quality associated with the twin-T ringing circuits used for percussive synthesis in this unit. Still, a big plus of the Master Rhythm is that all the sounds can be tailored to individual taste via level and resonance presets on the instrumentation board. Such adjustments used to entail poking about inside the unit, but the Master Rhythm now comes with holes conveniently situated beneath the presets for easy screwdriver adjustment from the outside of the case. This also makes it much easier to adjust the drum sounds when the unit is ensconced within the Band-Box. The length of rhythm sequences varies from twelve measures to thirty-two according to the position of the Rhythm Select control, but this is effectively doubled by each section being split into two sequence bins, A and B. Each bin can be played entirely independently or else the Sequence control can be set to program three alternative modes of sequence looping, i.e., A+B, 3A+B, or 7A+B.

All in all, the variety of instrumentation and generous length and number of sequences makes for a very flexible drum machine. I've always thought that mastering rhythms is a better policy than doctoring them, and the Master Rhythm proves my point!

As a stand-alone unit, the Master Rhythm runs quite happily off its own batteries for a good length of time (the blessings of CMOS RAM). Confined within the Band-Box, the Master Rhythm can follow the dictum of 'when in Rome, do as the Romans do' by turning its attention to the Band-Box's power supply. Alternatively, it can remain independent as far as juice is concerned. The advantage of that is that rhythms remain intact if the Master Rhythm is removed by Caesarian section from the Band-Box. Also, the 6V batteries in the Master Rhythm gives a larger op-amp output swing (desirable for percussive sounds) than the 5V Band-Box PSU. Decisions, decisions. Talking of deliveries, an umbilical cord also comes into the picture when the Master Rhythm is kicking away inside the Band-Box. In fact, there's a 7-pin DIN socket on the front of the Master Rhythm which provides some essential communications with the Band-Box circuitry, i.e., the all-important clock pulse (one per measure), a Start pulse, Rest and Play signals, rhythm pulses from the long cymbal control circuitry, and an audio output. The rhythm pulses are actually used to trigger the chord instrument that's synthesised digitally by the Band-Box, but more on that anon. The outputs from the socket can also be used with the Master Rhythm alone to provide clock pulses for one sequencer, rhythm pulses for another, and Play/Rest footswitch connections. Very useful!

Boxing the Band

Unlike the analogue instrumentation of the Master Rhythm, the sounds generated by the Band-Box are wholly digital in origin. In fact, the synthetic principles are the same in any digital system, whether Band-Box, Emulator, Fairlight, or alphaSyntauri. What it all boils down to is that any periodic waveform (i.e., one that's pitched rather than plain noisy) can be represented by a string of numbers stored in memory as a waveform table. The table can consist of 1,024 12-bit numbers (as in the case of the Casheab synthesiser for the S-100 buss) or it can be just 64 8-bit numbers (as with the chord generation in the Band Box). In general, the more numbers in a waveform table the higher the frequencies that can be synthesised, and the larger the number of bits describing each number the better the quality. However, the vast majority of the current crop of digital instruments use 8-bit resolution in making up waveform tables, and that keeps most people happy. Regardless of the finicky details, the numbers eventually have to be turned into sounds of different pitches, and there are two ways of going about that. The first technique is to alter the rate at which the numbers are read out of memory (the sampling rate), i.e., a low sampling rate gives a low pitch and a high sampling rate gives a high pitch. That's the principle behind the Fairlight and the Emulator. The alternative approach, and the one used by the Band-Box, is to read outnumbers at a constant rate but skip some values to shorten the effective length of the table. That ploy has the same effect as increasing the sampling rate, i.e., the pitch goes up. Turning these numbers into pitches is then just a matter of sending the stream of data into a digital-to-analogue converter and filtering the output into a nice, smooth waveform.

Well, that's a brief digression from the real matter in hand — explaining how one uses the Band-Box and what it sounds like — but these principles are here to stay and one might as well get used to them. The sound quality of the Band-Box is actually very good (it's certainly pretty quiet as regards noise), but there are certain limitations. Firstly, the sounds are static waveforms (a choice of four for both the chord and bass instruments) with an envelope imposed on top (again, a choice of four from the appropriate front panel switches). This gives a fair variety of sounds, but waveforms with no harmonic shifts during the course of the envelope do have an organ-like quality. As it happens, that sort of quality is quite appropriate for the instruments that the Band-Box is attempting to synthesise, i.e., string/electric bass and electric piano/organ chords, so one doesn't feel as if one's missing out on much. The one addition that would help animate the sounds is something like delayed vibrato, but there are FX units on the market which do this, and post-synthesis treatment of sounds may be a better plan of action than trying to force more out of the hard-worked processor in the Band-Box. The second limitation of restricted bandwidth isn't quite as apparent as one might think it should be, and that's probably for the simple reason that one doesn't normally expect a bass instrument to do anything other than utter the more-or-less occasional Deep Thought. Putting this into figures, the bass compass is limited to sixteen notes (F1 to G2) from 44Hz to 104Hz. Obviously, there are harmonics on top of these fundamental frequencies, but the low sampling rate (5kHz) and low cut-off frequency (700Hz) of the low-pass filter on the output means that you lose out on the highs.

Moving to the chord department of the Band-Box, one finds a range of eighteen notes (E3 to A4) from 165Hz to 440Hz, and the cut-off occurs at 1.6kHz. Again, this restricts the brightness of the sounds, but that's the necessary trade-off if one wants reasonably clean sounds from a digital synthesis system working at low sampling rates.

Putting the whole shishkaboodle of drums, bass, and chord instrument together makes for a pretty impressive combination, and the cymbals and snare certainly help to fill in the top end of the spectrum. All three members of the synthetic backing trio are given separate level controls and outputs (though a mixed output is also provided) and this offers plenty of scope for positioning and treating the outputs within a stereo perspective.

Micro Composing

I've purposely left the most impressive side of the Band-Box — the composing facilities — to the last. The bass and chord instruments have to be fed with the right data at the right time, and that comes from the 'scores' entered into the Band-Box. The score memory (3.5K) is arranged as 35 pages of 100 lines or instructions per page, making a total of 3,500 lines. Each instruction typically consists of a chord type and the duration of that chord entered using the following format:

Line number: 0-99
Group: 0-11 (e.g. '0' for the top line of chords)
Column: 0-11, S., d., J., F. (e.g. '6' to select an Am chord from the 0th group)
Value: 1-8 (in terms of measures from the Master Rhythm clock)

These instructions are entered using the numeric keys on the front panel in conjunction with the Enter and Compose (>) keys, and an 8-digit display provides some all-important visual feedback. In fact, there are two sets of numeric keys: those above the chord chart and the main set below the display. Judging by the layout of the keys, it'd be fair to make the assumption that the chord chart keys are specifically for composing, but they're actually just paralleled with the main input keys. I found this rather confusing, and, anyway, it's much more convenient to use the main set for instructions because of their proximity to the Entry and Compose keys (which actually enter instructions into memory). However, it's not quite an either/or input situation because some composing key functions (10, 11, S., d., J., and F.) don't get duplicated by the main set, and one ends up with flying fingers willynilly. Maybe that's making a mountain out of a molehill, but, as anyone with a ZX81 will know, ergonomics are the name of the game when it comes to entering lots of data, and I'd much prefer to see a single set of input keys with a decent amount of spacing between them. Entering chords is one side of the input story, but the composing facilities of the Band-Box also allow tacet bars (using the F. key) and segno/dal segno loops (using, respectively, the S. and d. keys) to be programmed. Such loops will then keep on repeating until the Coda button (or footswitch) is pressed, in which case the Band-Box will move on to the next instruction after the dal segno.

If there's any stream to be crossed in getting accustomed to the Band-Box, it's the somewhat overwhelming choice of chords. Still, better too many than too few! The column/group method of choosing chords is intelligent, but it does take time to learn where the chords are and what some of them actually sound like. It'd certainly be very helpful to be able to hear the Band-Box's interpretation of a chord at the input stage before committing it into memory. Entering a chord into the Band-Box only programs the harmonic flavour and duration, not the actual rhythm with which it's played. That crucial element comes from the Master Rhythm, courtesy of the long cymbal rhythm pulse, and it seems a sensible way of going about chordal animation — particularly because, whichever rhythm pattern is selected, the chords will then be played with the appropriate rhythm from the long cymbal track. However, unlike the drums and their accent control, the chord rhythm pulse is just a stop/go signal, and the chords can't help but sound a little lacking in esprit de parti. One can get around this a bit by using the right sort of envelope, but it still sounds a bit too regular for (my) comfort.

Though there's the Band-Box syntax to be learnt, entering scores is a pretty speedy process. Also, editing and reviewing is made very easy by the facility to scroll forwards and backwards through the lines of a score. As an example, the bars below took just 17 instructions (i.e., 17 lines) to enter into the Band-Box: 2-bar drum intro (bass and chords tacet), D///A7s/A7/D///A7s/A7/ Segno: Bm/// E7/// G/// A7///: Dal Segno D Finish.

The Band-Box actually comes with 20 or so preprogrammed 'classics' for instant playing, and the protocol for accessing these or your own scores is simply a matter of keying in the right index numbers (page number and starting line), pressing Play, and retreating after lighting the blue touchpaper. A logical place to start a score is on the 0th line of a page, but it can start anywhere within a page and go on for as many pages as your fingers feel like entering.

The first version of the Band-Box (or, rather, the first monitor ROM — the source of all the composing and synthesis routines) only provided preprogrammed bass patterns, but the latest software allows bass lines to be entered in roughly the same way as chords. Four bass programs can be entered, with up to 20 instructions in the case of three of them and 170 for the fourth, and are selected on playback from the Bass Figure switch. For each bass instruction, four notes are available from each chord. Generally, these follow the options of root, third, fifth, and sixth or seventh. The other instruction needed to define a bass line is the time interval (in ½ measures) between one note and the next. Again, all this is done by using the input keys in conjunction with the Enter and Compose keys. I rather like the sound of the Band-Box's bass, and, with the added facility to program in your own bass lines, it's made even more attractive. In fact, by programming in the right chords (which needn't be actually heard), it's possible to make the bass play exactly the notes you want for a bit of demonic bass solo.


The most obvious user of the Band-Box is the solo artiste (indeed, I gather that a good percentage of units have gone in that direction), but I think there's also a lot of general electro-music potential in it. The backing trio concept of the Band-Box can't fail to raise the hackles of some people in the MU, but a fine counter-argument is that such a unit gives musicians and singers the chance to perform without the financial headaches of organizing a band.

Like the Master Rhythm, the Band-Box is available as a kit (£314 as against £439 for the assembled version), and, according to Clef, "if you can build the Master Rhythm, then the Band-Box shouldn't be any problem". Anyway, whichever option one chooses, it does seem good value for money. Also, it's extremely reassuring to know that the unit won't stop here as far as improvements/additions are concerned. An add-on memory board (to expand the score memory to 9,000 lines) is very much in the pipeline, and, amongst other rumours I've heard, there's also an intention to widen the range of sounds available for the bass and chord instruments.

The Computer Band-Box costs £439 and is available direct from Clef Products (Electronics) Ltd., (Contact Details).

Table 1: Master Rhythm instrumentation

One Bass Drum Bass Drum Bass Drum
Two Low Tom-tom Low Tom-tom Conga Drum
Three HighTom-tom HighTom-tom Low Bongo
Four Snare Drum Long Brush High Bongo
Five Rim Shot Short Brush Claves
Six Long Cymbal Long Cymbal Long Cymbal
Seven Short Cymbal Short Cymbal Short Cymbal
Eight Accent Accent Accent

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


Electronics & Music Maker - Jan 1983

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Sound Module > Clef > Computer Band-Box

Review by David Ellis

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