"MMC" stands for "MIDI Machine Control," and it allows multiple MIDI-connected devices to interact and control each other. Setting the "Transport mode" to a setting other than "None" allows it be controlled by MMC messages.
None : will have Qtractor ignore incoming MMC messages, and not provide outgoing MMC messages
Input : will have Qtractor follow incoming MMC instructions, but not provide outgoing MMC messages
Output : will have Qtractor ignore incoming MMS messages, but provide outgoing MMC messages
Duplex : will have Qtractor follow incoming MMC instructions, and provide outgoing MMC messages
You can also select a particular MIDI device number with which
Qtractor will interact; if you do this, it will ignore MMC messages from other devices, and not send MMC messages to other devices. Enabled the "Dedicated MIDI control input/output" will provide JACK with MIDI inputs and outputs that will be used by
Qtractor only for MMC messages.
Qtractor will not send or receive MMC messages sent on other inputs or outputs if this option is enabled. "SPP" stands for "Song Position Pointer," and helps MIDI-connected applications to keep track of the current location in a session (in other words, where the transport is). This should probably be set to the same setting as "MMC." If you don't know which of these settings to use, then setting "MMC" to "None" is a good choice. This setting can be adjusted at any time, if you later decide to link applications with MMC messages.
The default metronome sound is provided by the "MIDI Metronome," and you can adjust its settings here. In particular, you may wish to provide a "Dedicated MIDI metronome output," to help you separate the metronome's signal.
