Re: Repeater and sync from midi in

[Chris Muir <cbm@well.com>]

Title: Re: Repeater and sync from midi in

At 4:30 PM -0400 7/19/03, Paul Sanders wrote:

> I suppose that's true, but the notion
> that, one is going to get *something*
> from a device (in this case the midi clock from a drum machine) so, it
> makes
> sense they should be on the *same* midi channel isn't unreasonable
> IMO. The
> notion that "I need to get the midi clock from this drum machin,
> so let me
> make sure I set it to a *different*
> channel" is less than intuitive.

I suppose that's true, but the notion that you can get anything useful from a fairly complex system without understanding at least some of the basics isn't reasonable, IMO.

A basic concept of MIDI is that there are two types of message, Channel and System.

All the Channel Messages have embedded channel information in them. Channel Messages are further broken down into Channel Voice (e.g. NoteOn, Controller) and Channel Mode (e.g. LocalControl) messages.

System Messages are global and have no channel info in them. System Messages are broken down into System Common (e.g. SongPositionPointer), System Realtime (e.g. Clock, Start, Stop) and System Exclusive (i.e. manufacturer-specific stuff) messages.

Don't let your preconceptions about how a system is supposed to work get in the way of your learning how the system really _does_ work. Google (or similar) should turn up quite a lot of references and tutorials. The British magazine Sound on Sound had a rather good series, but this was several years back. It may well be on their web site.

> I've seen other posts from people getting
> bit by this, and others who have
> "worked around" it but not really understood exactly what
> the problem is.
> It's a bit obscure an could be documented
> better. Much better.

Now I don't want to be cast as a MIDI apologist. I've been pretty outspoken on my dislike of many aspects of MIDI's design over the years. But that hasn't stopped me from understanding and using it for a long time.

I think that one of Kim's points is that your problems are not Electrix's fault. The Repeater has a fairly good MIDI implementation. It works in a way that makes sense to people "schooled in the art". The problems that you've mentioned, so far seem to be problems of your internal concept of MIDI not matching the reality of MIDI.

Just like your compilers don't teach you how the C language works, it is not Electrix's job to teach you MIDI.

> I'm just now coming in on all this MIDI
> stuff though in the past few days
> I've learned most of what I've been after. I guess those who have
> been
> dealing with it for some time have more of a "well DUH!"
> view of these
> things because they've know and lived with all these things for some
> time.
> I'm coming in with a fresh perspective. I guess though, it doesn't
> matter
> what my perspective is, it won't change
> anything.

If you feel that you have enough fresh insight into this, perhaps you should write up your findings so that other people new to the field can benefit from your experience.

> I just looked at this, and I fail to find
> the answer to my misunderstanding.
> I supposed if I were able to read betweent the lines a bit better it
> would
> be more useful.

I thought that this was pretty clear (near the top of page 34 in the manual):

> MIDI CHANNEL SELECTION
> Repeater receives MIDI information on the channel
> specified by the MIDI channel selector on the rear panel.  There
> is one exception to the global MIDI receive channel as set by the rear
> panel selector: MIDI clock messages are not channel specific and will
> be received regardless of the receive channel. Additionally, reception
> of MIDI Clock messages will not light up the MIDI Receive LED on the
> front of Repeater.

[re: UDP analogy]

Actually, I think that a slightly better analogy is a TCP/IP stack that has many well known ports which are open for many different protocols. There's port 80, ready to accept http traffic, port 25 open for SMTP traffic, etc.

All this data flows into this system, through the same wire, on top of UDP, but it has a different interpretation based on what protocol it is. The same rules don't apply from one protocol to another.

MIDI also roughly has the equivalent of different protocols traveling down the same cable: System and Channel.

Chris

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