You buy a machine because your drummer can't play in time, then find your machine won't play in sync...

There are many good reasons for programming the rhythm parts of a song on your drum machine. You may prefer playing the rhythm using the onboard pads or maybe it's just down to how easy you find the process of working with a drum machine. It may even be that the machine you're using has real-time playback qualities which cannot be conveyed over MIDI, such as slight timing or tonal variations to give your rhythm tracks a more 'human' feel.

But of course, other parts of your song are likely to be recorded on a sequencer, and irrespective of whether you program the rhythm part first or last, at some point you'll need to get the drum machine and sequencer to play in time with one another. Such a process is usually referred to as synchronisation, and it's usual to have the sequencer controlling the drum machine's playback timing. This means that the sequencer adopts the role of the master and the drum machine becomes the slave.

In the early days of sequencing, synchronisation was achieved by a master device sending out an audio pulse each time it moved from one sequencer step to the next. On receiving this pulse, the slave would do likewise and so keep in 'sync' with its master. In a MIDI system, the pulse is provided by a special MIDI message called a MIDI Clock and for this to be received by the drum machine, the MIDI Out from the sequencer has to be connected to the MIDI In of the drum machine with the sequencer's MIDI Sync Out and the drum machine's MIDI Sync Receive functions being turned on.

The configuration of this system is shown in Figure 1, and you'll notice that various messages are used to keep the two devices in sync. Have a look at the Glossary for detailed explanations of these.

So how do you connect a drum machine into your system? Take a look at Figure 2 which includes the common configuration of synth, sequencer, sound expander and drum machine. Here you'll see that the MIDI Out from the synth connects to the MIDI In of the sequencer so that notes and other MIDI performance information can be recorded. The MIDI Out from the sequencer then connects to the MIDI In of a MIDI Thru box so that MIDI information can be distributed to all other units of the system - although you could use a daisy chain arrangement here if you wish (Figure 3).

While the keyboard and sound expander need to get the note and performance information intended for them, the drum machine only needs the MIDI Sync messages. And, while the sound-generating members of the system will ignore these sync messages, the drum machine may well react to the incoming MIDI notes. This was explained in Part 4 of MIDI By Example and to ensure that this doesn't happen, you'll need to check that that the MIDI Note Receive (or similar function) on the drum machine is turned off.

What happens if you want to play a sequencer and multi-track tape recorder in sync? Well, that's another story...