Elektron Musical Instruments

Since I got the Mono, I've begun realising what a great piece of 
machinery the MD must be. I'm seriously thinking of buying one.

In the Mono manual Elektron tells us that we should use the Mono as 
base because of the tight clock. If I buy an MD, how will I set that 
up with the Mono and a third synth? I like having the Mono's six 
sequencer tracks sequencing the third synth, will I have to use one 
of them to control the MD, or can I somehow use the MD to trigger the 
Mono?