Midi playing speed

[busker99]

I now hava a good dout card using midio128 and have applied this to my pipe organ with the aid of some solenoid valves in the wind chest. I now want to vary the speed that the midi tune is played either by a varying voltage or varying frequency pulses. With this, I can make the tune respond to the speed of the crank handle for the bellows. I'm not sure if this is a function of the midio128 program, or whether I must look to the player system. I know the commercial organ systems can do this. Does anyone have any ideas on this ?

[stryd_one]

MIDIO128 is just converting MIDI to digital signals to drive the organ - you'll need to change the tempo in your midi sequencer/player.

[lylehaze]

The tempo of a MIDI file is defined in a Tempo meta-event, as part of the MIDI file format. You can learn all about it here:

http://home.roadrunner.com/~jgglatt/tech/midifile/tempo.htm

So to "play" with the tempo, there are two approaches:

You can add a bunch of tempo change meta-events to your MIDI file. This would work only if you knew in advance what all the changes are.. OR

You can Synchronize your sequencer to an external clock, and then all you need to do is to create MIDI clocks by hand as you go.

http://home.roadrunner.com/~jgglatt/tech/midispec/clock.htm

This would allow "live" playing with the playback rate.

Something like this COULD be made with a core and a encoder, using the pulses from the encoder to trigger the clock messages. You would probably also want buttons for start-stop-song position-song select-whatever else.

Sounds like fun,

LyleHaze

[busker99]

Thank you, LyleHaze, for your quick response and your suggestions.

I use a small Palm Vx to operate the dout card and "fiddling " with this is definately a non starter. It takes a hair dryer to even open it as it's glued together ! I looked at your links for sequencers and it seems that they are software devices. I can use cakewalk to play the files and alter the tempo 'live' but I really need something to respond to an external, mechanical / electronic signal. It seems that another type of player is needed. I have been looking at the SD Card reader player which is an open source device on the web. Maybe this can be tweaked to produce the desired effects.

Thanks again

[lylehaze]

Those links are actually to a site that documents the MIDI standard(s). While I have never used Cakewalk, I would be very suprised if it could not synch to an extrnal MIDI clock. What you would need is something like:

The Bellows crank turns a low-resolution encoder.

A MIDIBox core reads the encoder, possibly scaling it, and transmits MIDI CLOCK events every (n) pulses.

The MIDI OUT from that core connects to a MIDI IN for Cakewalk.

Cakewalk has the desired MIDI file loaded, and is set to follow an external MIDI clock.

CakeWalk drives MIDI OUT To the same (or a separate) Core that controls the DOUT module(s) that drive your organ.

At least, if I understand your question.. but maybe I've got it wrong.

Have Fun,

LyleHaze

If you want it "all in one", you will need to write a Format zero MIDI file player (I have a code that will get you started), and you will need some kind of storage for your MIDI file(s).

If I were you, I'd start with doing it through cakewalk first, to get that part ironed out before going forward.

[edit] matched process to details in the original post.