[linux-audio-user] MIDI toots

[Allan Klinbail]

Hi Felipe

I can't direct you to a good tutorial on MIDI but I can give you a brief
of what it is all about. 

MIDI is about control, it's simply a protocol that came about in the
late 70's early 80's when synths started getting digital onboard
controllers and then had digital engines made. For some freak unknown
reason all the hardware manufacturers actually agreed on a standard. 

The simplest form of MIDI messages are "note on" and "note off"... a
sequencer or MIDI player can tell a synthesizer when to turn a
particular note on and when to turn it off. 

On top of this message other parameters can be associated such as
velocity (how hard you hit the piano key), volume, aftertouch (how you 
release the key). 

The next level are the controllers, each channel (oops there are 16
channels per MIDI port) has 127 controllers... some of these are
predetermined (such as the volume, modulation wheel, e.t.c..)and others
are assignable, some synthesizers have more parameters, (LFO's, filters,
e.t.c.)  than others and these are often given controller channels.

The final level of MIDI are the timing controllers.. this is what  most
people talk about with reference to hard disk recorders and external
sequencers... There are 3 types of timing control. 

MMC, Midi Machine Control... essentially Start, Stop, Resume
Midi Clock... tells the device Beats per Minute
MTC (aka SMPTE) which gives a real time reference in minutes seconds and
frames... (essentially used for video sync) 

These last 3 protocols are extremely important when using more than one
device that requires time.. i.e. in my rig I have an external sequencer,
a drum machine, a time based effects unit and of course the computer.
When recordong or playing it is essential that these are all in sync..
with MMC and Midi Clock, I can control everything with the external
sequencer.. The BPM are set by the external sequencer and I can use the
start and stop button on the sequencer and everything begins and stays
in sync. 

So MIDI is essential in a professional studio where any external
synthesizers, samplers, sequencers or devices that need time code are
being used. Internally within a PC you could use it to say drive a soft
synth with a software sequencer using internal MIDI routing. This is
really only a cursory look at MIDI and there are more in-depth resources
to look at. However I think you can see it's a little more useful than
distributing tunes for karaoke. 

cheers

Allan     



On Tue, 2003-06-10 at 09:41, felipe wrote:
> Hi all,
> 
> Ok I've been avoiding MIDI for too long... I just used ecasound and now ardour 
> + hydrogen to "fix" some ideas on the HD for later experimentation with my 
> band. Now I'm starting to feel curious about MIDI (those MTC and MMC commands 
> in ardour?!?).
> 
> The question is: where do I find some good tutorial or manual covering the 
> basis of MIDI? And: what do you use MIDI for? I thought it was all about 
> karaoke and the such...
> 
> Thank you
> 
> felipe
> 
> 
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