MIDI Machine Control This Clock setting allows Metro to send MIDI Machine Control (MMC) commands when syncing to SMPTE/MTC. If you have a tape deck or hard disk recorder that supports MMC, this setting eliminates the need to start Metro’s transport and then start the sync source. When you hit play in Metro, it will go into sync mode as above, and it will also start the clock source machine. For more info on the MMC window, see the section in Chapter 11.