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Conference napalm::commusic_v1

Title:* * Computer Music, MIDI, and Related Topics * *
Notice:Conference has been write-locked. Use new version.
Moderator:DYPSS1::SCHAFER
Created:Thu Feb 20 1986
Last Modified:Mon Aug 29 1994
Last Successful Update:Fri Jun 06 1997
Number of topics:2852
Total number of notes:33157

297.0. "Yamaha DX7 MIDI Quirk" by NOVA::RAVAN () Tue Apr 08 1986 05:20

    I've just started writing some MIDI software for my DX-7.  I have
    a problem which is probably well-known to anyone who has tried to
    do so on any computer.  When the DX-7 powers up, it sends an active
    sensing message, followed (after the active sensing message 'times
    out', I believe) by note off commands for all its notes, and then it
    goes into a loop sending 'system exclusive, YAMAHA-manufacturer-ID'
    bytes.  Note that the sys-ex-YAMAHA bytes are not followed by a
    EOX (end system exclusive) byte as per the V1.0 standard.  John
    Sauter told me that this was known to be a quirk of the DX-7 since
    it was one of the first synths to implement MIDI and got it wrong.
    
    I have two questions:
    
    1)	How can I tell the DX-7 that MIDI is alive and well, so please
    	be quiet?
    
    2)	I thought (maybe I'm wrong) that an active sensing message didn't
    	'time out' and cause a synth to do any kind of output, but instead
    	just caused the synthesizer to assume some manufacturer-defined
    	configuration and 'stand-by'.  Am I wrong, or is this yet another
    	case where Yamaha misinterpreted the spec?
                              
    -jim
T.RTitleUserPersonal
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297.1My ContributionDSSDEV::SAUTERJohn SauterTue Apr 08 1986 11:1718
    I am not as sure if my facts as .0 implies.  I have only "seen"
    a DX-7 through a Roland MPU-401, whereas Jim is looking directly
    at the MIDI bus.
    
    My DX-7 and its literature is out on loan, so I can't check the
    documentation, but I think the device sends "active sensing" all
    the time.  If it receives "active sensing" it goes into a mode
    in which if it stops receiving "active sensing" it shuts up.
    This is to avoid having a note stuck on if the cable is pulled.
    
    I think the ``sys-ex, Yamaha'' messages are another "keep-alive"
    message used for the same purpose.  I seem to recall a hack in
    some of the intelligent interfaces to allow for this message,
    since it doesn't terminate properly.
    
    The note offs I find very strange.  I hope somebody has some
    experience in this area to share with Jim.
        John Sauter