The Prophet from Silicon Valley: The complete story of Sequential Circuits by Unknown

Author:Unknown [Неизв.]
Language: eng
Format: epub
Publisher: AM Publishing New Zealand
Published: 2015-07-03T22:00:00+00:00

The development of MIDI

Dave Smith was very much aware, even before the Prophet-5, of the incompatibility of different brands, from his experience of making the 700 Programmer and 800 Sequencer. Indeed, the operating manuals of both these machines detailed how to connect control lines to various brands of keyboards. Some connections could get quite involved, connecting the 700 Programmer to the Minimoog, for example (see Chapter 1).

Sequential’s pre-MIDI digital communication protocol was first conceived when fitting the dual-manual Prophet-10 with a sequencer. The synth was fitted with a universal synchronous asynchronous receive transmit (USART) chip to allow data transfer between the keyboard and the sequencer. The data format was serial and worked by updating note status on a regular basis as set by the sequencer’s clock frequency. In 1981, the system was added to the Rev 3.2 Prophet-5 to interface the Prophet Remote and the Poly-Sequencer to it (see Chapter 7).

Sequential published its serial data protocol in the Rev 3.2 upgrade instruction paper and openly encouraged the technically minded to explore their own uses of the interface. However, the general feedback suggested that the protocol in its present form required programming at a low level and used a lot of transparent or superfluous data. When it came to thinking about a universal interface, Sequential recognized the need for a more concise data protocol and to keep it simple, while at the same time, covering the most common synth functions.

Meanwhile, Oberheim had its Oberheim System on the market, consisting of a parallel interconnection between their OBXa synth, DSX sequencer and DMX drum machine. It was later added to the OB8 synth and DX drum machine. Roland brought out its digital control bus (DCB) serial interface in 1982 and added it to the Jupiter 8 and Juno 60 synths and JSQ-60 and MSQ-700 sequencers. Also, Rhodes had a parallel interface built into the Chroma to connect it to the Apple IIe computer, and Yamaha had developed its YMCS (Yamaha Music Communications System).

The first discussions for a common interface began at the NAMM show in Chicago, June 1981. Roland founder and president Ikutaro Kakehashi discussed the idea with Tom Oberheim. Tom then mentioned it to Dave Smith, and after the show the Sequential team discussed the concept further. All agreed that a universal digital interface was a good idea, so over the next few weeks, Smith came up with a revised serial protocol. The main differences between the Rev 3.2 interface and the revised one was that the 3.2 was continuously polled, whereas the revised one only sent data when a change occurred, and the data rate was reduced from a continuous 625kHz to a baud rate of 19.2kbps (kilobits per second).

Design engineer Paul Rutigliano recalls his involvement in the early phases of MIDI development. “I worked on MIDI. And they decided that the industry needed a common interface. Things in those days were pretty small scale. So Dave was the main contact and he’d come back and say, ‘Here, I want you to look into this.

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