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Technically Speaking (Part 1)

This month's project, rescue your old synthesisers with a MIDI to control voltage converter. That Andy Honeybone, he's a life saver, eh? But first, a few words on the wise spending of dosh where synthesisers are concerned.

SOME MIGHT argue that if the biggest problem you have is how best to spend £1500 on musical 'toys' then, in worldly terms, you have no problem at all.

Homespun philosophy aside, I'd like to slow the pace a little (to a fast jog) to comment on the technical side of the new releases from the trade fairs while also introducing this month's retrospective programming project which is a MIDI to control voltage converter. Somewhere along the way I'd also like to add a few words about the FORTH language and BBC micro for the benefit of our new found overseas readers.

The most upsetting aspect of the announcement of new kit is the feeling of injured pride for those owners of the superceded items. The electronic musical instrument business is known for having a fairly short product life — variously quoted at around 15 months. The DX7 was something of a rarity with a four year run, but as night follows day, the mark II is now with us.

Early owners of the Mirage have had to put up with witnessing a series of price cuts and now, apparently, the most recent reduction comes with re-styling. But at least software updates have been available even though as an outsider, those revisions would appear to have been essential rather than just niceties.

Writers on the subject of new musical hardware do have a hard job trying to dig out the facts from the pre-release bumpf. By the time that the things can be fully appraised, they are no longer the hot news that they were at their announcement. A case in point is the TX81Z. The common theme/smokescreen is that this unit is an upmarket FB-01. Extra peeved then must be those owners of effbees who may only just have managed to obtain theirs in the last couple of months — many months after its announcement before last year's BMF.

But is the TX81Z that much better? The British press all state that the TX is eight voice but a leading American magazine reckons on 16. The same magazine also says that the TX is 12 bit to the effbee's 10. Time will tell.

Several new technologies or at least synthesis models have emerged. Roland's D50 digital-linear synth and Korg's DS8 'easy FM' machine have joined the ranks of the wavetable oscillators of the ESQ1 and Sequential's vector synthesis. The search for a cheap-to-produce alternative to the definitive discreet component Oberheim analogues and the 'too difficult to program' FM digitals is obviously moving on.

Now is not the time to buy a sampler. Buy expensive and you'll see prices tumble: buy cheap and you'll end up with an unexpressive beast with a tedious appetite for discs. Why do they use those Quick Discs? Well, they're cheap and robust and OK when true random access isn't required. Six sides to load a multi-sampled piano is still hard to swallow. If sampling wasn't such an 'in thing' would you seriously buy a synthesiser with only six voices instantly available? I still want one though.

Having been through the introspective homemade album trip a few years back and thereafter embraced the world of live performance, I've studiously avoided the acquisition of a personal multitracker. One of the many catchpenny aspects of MIDI is the notion that you should own enough synthesisers to respond to every channel to the polyphonic limit of your sequencer. In this way you can 'put everything down in one'. The flaw in this argument is that in order to capture every nuance of performance you will require a sequencer of enormous memory capacity — a 30 second 'orchestral jingle' might just fit in a QX5. In this light, a multi-track recorder does seem rather sensible, not only saving the price of an Atari + package but also a bank of space consuming synthesisers. Multitrackers are established technology and you get what you pay for. They probably represent the most durable purchase you can make. Having said all that, I can't get excited.

So what are the Honeybone rules for buying without too many tears? Firstly, don't. Cynical advice to swallow, perhaps, but I know you won't heed it anyway. The point is that something better will always come along so you want to be very sure that your present kit is seriously hampering your creativity before you consider a change and the ensuing parting-with-dosh. Secondly, acquire a reasonable master keyboard early on. There are many rack mount versions of the latest stuff available at reduced prices. Third, ensure that sound sources are at least bi-timbral even if not fully multi-timbral. Velocity sensitivity is also a must. This will enhance their use as an expander when relegated. Fourthly, if the unit has a disc drive, hold out for 3.5 inch format. Can you buy Quick Discs at Argos? (no). Disappearance will be the only thing that the 2.8 inch horrors will be quick at. Fifth, don't buy a drum machine that can't dump patterns over MIDI. One day you may have a computer, MDF1 or DX7IIFD. Lastly, if you want a sampler, think 16 bit.

Well, that's my entry for digression of the century.

The code presented above is for a MIDI to control voltage converter. Because it needs some hardware in the shape of the digital to analogue chip and trigger interface, I've held those over till next time along with the code description. Those clever dicks among you who can throw a converter onto the Beeb's user port will be able to get it up and running straight away. The program features note priority switchable between the highest note and the last note pressed. The former is useful for ghosting the top melody line when the driver and analogue synth have dissimilar sounds, while the latter fattens up a digital synth when similar timbres are selected. The converter has a five octave range but this could be easily extended.

And to whom it may concern, the code is written in Acornsoft FORTH which is a FORTH-79 implementation for the Acorn BBC 'B' microcomputer which is 6502 based and has 32k memory. The FORTH resides in ROM to release maximum RAM. The listing was prepared using the VIEW wordprocessor and may either be sectioned to fit onto multiple 16 line FORTH screens or may be 'spooled' in directly using the OS' EXEC «filename» instruction. The MIDI interface appeared in issues 1 and 2 of MAKING MUSIC but may be substituted with any 6850 ACIA based interface (E&MM, ETI, etc) with suitable editing of the addresses declared as constants at the head of the listing. The interrupt line of the ACIA must be connected to the non-maskable interrupt of the micro. Good luck.

(Click image for higher resolution version)

Part two of this project will be in next month's issue.

Series - "BBC MIDI To CV Convertor"

Read the next part in this series:

All parts in this series:

Part 1 (Viewing) | Part 2

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Patchbay Power

Making Music - Copyright: Track Record Publishing Ltd, Nexus Media Ltd.


Making Music - May 1987



Electronics / Build



BBC MIDI To CV Convertor

Part 1 (Viewing) | Part 2

Feedback by Andy Honeybone

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