The MIDI clock protocol was created after the general MIDI protocol, as musicians realized they needed an automatic metronome mechanism to keep MIDI instruments in sync. Most MIDI devices now include a clock function and the ability to be MIDI slave or master, in relation to other devices. The simplest form of clock is the MIDI Time Code clock. MTC transmissions contain simple time and beat information. A more complex form of MIDI clock, called MIDI Machine Control, is used to control digital recorders from a master device. Akai’s MPC samplers can send and receive both types of MIDI clock.
To properly set up an MPC with Pro Tools, you must use the correct MIDI clock type in the correct context. For example, to use the MPC as a master device in relation to Pro Tools, set the Pro Tools’ clock to receive MTC transmissions on any reader port. Set the MPC to send MTC transmissions. MMA transmissions from the MPC must also be turned on. The opposite setup is required to slave the MPC to Pro Tools. If the setup is not performed correctly, the MPC will experience synchronization problems with Pro Tools and will not play back correctly.
For an MPC to correctly synchronize with Pro Tools, you need to create at least one bar of pre-roll on the MPC to send to Pro Tools. Some users skip this step, resulting in incomplete or stilted playback from the MPC. “Pre-roll” is at least one musical bar containing random MIDI note information that is inserted before an actual composition on the MPC. It helps MTC transmissions to correctly synchronize between machines. The same is true whether the MPC is MIDI slave or MIDI master in relation to Pro Tools.
If the MPC only plays a few notes in Pro Tools, for example, when attempting to use the MPC as a controller for a software drum sampler or vice versa, MIDI time clock synchronization may not be to blame. In some cases, the problem lies in incorrect or mismatched MIDI note mappings on the MPC. Some users create custom drum mappings on the MPC that may not correspond to the mappings required by the software sampler. As a result, playing the MPC’s pads during or after synchronization will produce incorrect sounds or no sound at all. The MPC’s pad mapping must be adjusted to correspond to the software sampler’s mappings to work correctly.