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The Chroma/Apple interface

Article from Electronics & Music Maker, March 1983

John Shykun talks about the new Chroma/Apple interface

John Shykun using the Chroma/Apple Set-up.

CBS Musical Instruments have just announced the release of an Apple II computer interface package for their Rhodes Chroma Synthesiser.

The interface kit includes a card which plugs into the Apple I/O Slot 1-7, connecting cables and software disks with sample sequences and program groups.

Communication between the Apple and Chroma is via two interrupt driven 8-bit parallel ports plus associated control signals.

A complete command set is provided allowing the Apple to query or set the status of the Chroma mainframe, control panel or any of the voices.

The interface can also be controlled by user-written programs in Applesoft or assembly language.

At a recent demonstration, E&MM met John Shykun, Director of Marketing for Rhodes Keyboards. Here he talks in detail about the new package and what it offers the Chroma user.

"The Apple II interface is the first of four computer interfaces we'll be releasing this year which also include the new 16-bit IBM, the TRS-80 and the Commodore 64. Our Apple software will be compatible with the Apple IIe.

We chose the Apple II because it's possibilities are so wide but the IBM micro should be a very good system for educational and extended use. I think that some computers, however, will turn out to be better suited to music than others, and we have high hopes for music applications with the low cost Commodore."

Pressure Sensor addition

"We've just finished evaluating the pressure sensor. The public have seen it at the Anaheim exhibition, and Herbie Hancock, Ian Underwood, Victor Feldman and a few other well known people played it and were very happy with it. So we're now going into pilot production and should have it available in the next few weeks. The sensor replaces the damper element of the Chroma keyboard. It takes only around 20 minutes to install as there's already a place inside the machine for it, and it gives individual pressure sensoring for each key — all independent, so it's not like pitch bend. Now you can bend one note or chord and not the others.

My part in the development of the Chroma has been as 'resident musician' so to speak. To help with the musical and human part of the machine: where everything's going to go, how it feels, the placement of the knobs and switches, and the input of the software, how friendly it could be or should be. It's something that's a continuing role, not only for the Chroma, but for the instruments that will follow.

The actual touch panels were chosen to save on cost and they were developed before Gulbransen organs used them. I've not had so much to do with the software as with other parts of the instrument. We have one guy who's head of our applications group, Tony Williams in Holborn, who is writing up the basic application software. Now, as we get more into 'user friendly' software, I'm becoming more involved with the way the manuals should be worded for musicians. We still have a long way to go there. The first micro interfacing software for the Apple II was done in both Applesoft and Assembly code. From now on, however, we're going to do it in Pascal so that we can drop it easily into the different computers.

Now we've got the funding, and now we've seen the pathway to this computer market — the most asked for second request of users being musical applications — we want to be able to contribute to that. I went to the Consumer Electronics Show in Las Vegas and there were two systems up and running there, admittedly very primitive, but a beginning. Also, Commodore are showing a peripheral keyboard for their 4-voice system on board. But I think the big advantage we hold in the music business, in addition to the experience we have from micro-based musical instruments and their software, is that the 'sonic' capabilities that we possess on our machines are far superior to the equipment they're showing. So we have a lot of interest, in fact CBS in general has a very great interest in this area now, and they're making funds available to do their own software. So that will speed up the process of making more and more computers available to the Chroma."

Analogue to digital control

"Manipulating the knobs for the new instruments is sort of akin to the solid-state/tube amplifier thing that happened. It's going to be that kind of transition and we're going to be going through a lot of learning processes. On the Chroma a guy, or gal, is going to see one parameter at a time, but the list of parameters is almost endless that he's got control over. If we wanted to put a knob or a slider for every one of those controls, we could have put them there, but there'd be a hundred sliders on the Chroma panel and the cost of the instrument would drive it away from everybody who would want to buy it anyway. So it was a trade-off that we accepted, knowing full well that later on these computer type applications would help us solve some of these problems.

The VDU display will show full parameter functions on the screen, in effect putting the full programming manual on disk. So we feel that this is something we're going to work our way out of. There's been resistance, certainly, to the machine, although it hasn't been as negative a thing as I'd have imagined.

I do think the main slider controller ought to be a wheel, with no polarity at all — just wherever you started, it picks up again. The mechanical thumper doesn't seem to cause problems since normally you're amplifying the machine and it doesn't come through the amplifier system. There are many more musical functions in the Chroma available than are accessible at the moment. There's also a separate computer inside for the keyboard scanning. It will allow attack or release times to be actuated on both the down stroke and the up stroke or attack structures both up and down. It requires technical procedures that nobody has actually done before, so you have to develop new techniques to play some of these things. In addition to the things you expect velocity sensors to do, which it does quite well, it also does things which keyboards have never done before, so it'll be a matter of how people create with them."

Interfacing Chroma

"Referring to the Apple II specifically, the present software (which is one of several sets we're releasing over the next few months) allows you to do multitrack sequencing. The Chroma is a 16-channel synthesiser with each channel basically a little one oscillator, one filter, one VCA, two envelope synthesiser. The Apple is capable of seeing it that way. It lets you organise not only polyphonic synthesis of any kind, but also multi-timbral synthesis. Basically, you're able to use the Apple as a solid-state 16-track recorder and all performance information, whether it's velocity or pressure, the levers, the pedals, any parameter changes you make during the performance are sent over to the computer. It records the performance in the way that a tape would, so you can actually build any type of multitrack performance sequences, one track at anytime, can change volume level independent of others and it's possible to do many editing changes during your performance, including a complete re-mix.

The Apple II 48K model requires an extra 16K RAM card to operate, plus two disk drives. (The Apple IIe is already 64K.) Everything is stored on disk, including your program sounds and sequence information. Some 25 hundred to 3 thousand notes is a good average for the amount of notes available. A 3-minute piece can be accommodated quite easily. The number of tracks you use are not so much a problem as the actual duration of the piece. Memory is assigned initially but then a function will 'scrunch' everything down finding unused memory and moving it to the end of the sequence. An extra memory card will be available to extend memory to 10,000 notes average. If you're really clever and use loop functions a lot, you can do a lot more with the software.

What we're basically selling is hardware — the actual card that goes in, plus a function disk to show you the capabilities. But from this point on, anything we release for the Apple will be basically just 5¼" disks, with free software up-dates and disk exchange. The next one we have coming is a basic programming manual on disk showing the full graphics of programs and entire parameters on the screen.

Triggering for external drum machines is available for the Linn machine, DMX, Oberheim and the new Drumulator from EMU. There's a black box for the back of the Apple that we can supply. We're having some trouble linking basic analogue drums but digital are fine. The IBM micro will extend the multitracking options and give direct-to-disk storage — one of the things with Apple is that when you run out of notes (i.e. RAM), you've got to stop and dump to disk before continuing. Each micro will get its own relevant software, with the other three available by mid-'83.

I think we're going to see very much more 'intelligent' Chromas that are brighter and much more friendly, telling you what's going on inside them. The Chroma itself will not become outdated and whether you buy a Mark I or II, you'll be able to extend your instrument indefinitely."

For further details contact: CBS Fender Ltd, (Contact Details).

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Record Review

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Music Maker Equipment Scene

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

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Electronics & Music Maker - Mar 1983

Gear in this article:

Synthesizer > Rhodes > Chroma

Gear Tags:

Analog Synth

Feature by John Shykun

Previous article in this issue:

> Record Review

Next article in this issue:

> Music Maker Equipment Scene

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