jahrome wrote:The MPC line is the best hardware MIDI sequencers on the planet. There is no..I repeat..no timing issues when using it with MIDI sound modules. Take your pick...MPC 2000, 2000XL, 2500, or 3000. All solid in this regard from my experiences.
I am curious to know what you are talking about. There is no difference in timing whether I use internal drum sounds or sounds from external gear.
That is your experience, your ear, for the purposes of the music that you make.
I am only interested in facts, so I offer this:
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How Simultaneous Can Two MIDI Notes Be?
or
Time Is Nature's Way of Keeping Everything from Happening At Once
MIDI data sent on a MIDI cable are transmitted as serial data. A sequence of ones and zeros tells your drum machine to "play the sidestick on channel 3 mezzo forte." It takes a bit of time to transmit those ones and zeros. More important, all the information for one note must be transmitted before the next note can begin.
What is the delay between two "simultaneous" MIDI notes on a single cable? For those who just want the facts, the answer is 960 microseconds for ordinary Note On events or 640 microseconds for Running Status Note On events.
How do we get these numbers? Get out your calculator and follow along. The first thing to know is that MIDI data are transmitted at 31250 bits per second, also called 31.25 KiloBaud. (This peculiar number happens to be 1/16th of 1,000,000 cycles per second. Many early computers had built-in crystal oscillators running at this frequency; this was an easy frequency to derive.)
Each byte of MIDI date requires 10 bits of serial data. The byte is transmitted with one start bit, eight bits of real data, and one stop bit. The start and stop bits are needed to tell the receiving circuitry "here comes some data," and "that was the end of the data." At a rate of 31,250 bits per second, we can send 3,125 (31,250/10) of these "MIDI bytes" per second.
To send one Note On message requires three MIDI bytes. The first byte says that this is a Note On event and specifies which channel (1-16). The second byte says which key number is to be played. The third byte specifies the velocity. We can send 1042 (3,125/3) such Note On messages per second.
But we promised to tell you the duration of each Note On message, not the number of messages per second. This is easy: 1/1042 messages per second = .00096 seconds per message. In technospeak, this is .96 milliseconds, or 960 microseconds per Note On message.
MIDI does offer a slight speed improvement through Running Status messages. After sending a normal three-byte Note On message, a sequencer can send additional key number/velocity messages, omitting the first byte of an ordinary Note On message. For a string of notes that all occur on the same channel, this reduces the number of MIDI bytes per Note On message from three to two. We can send 1563 (3,125/2) Running Status Note On messages per second, which corresponds to .00064 (1/1563) seconds, .64 milliseconds, or 640 microseconds per message.
The bottom line is that for MIDI data running on a single MIDI cable imposes an absolute "speed limit" of about 1000 Note On messages per second, or 1500 Note On messages when Running Status is in effect. This number gets worse with other MIDI data, such as aftertouch and controller information. Your actual mileage may vary.
- Robert Poor
Director of Research and Development
Opcode Systems, Inc.
By Daniel C. Cantor, with Mark Weltner
Notable Productions@1994
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taken from
http://www.notable.com/index.php?page=about
