Mellotronists

Hi all, I need to find some information and I think asking the group is probably the quickest way of getting it. What equipment and what procedure would you need to have a sequencer play back in sync to a clock signal of some sort from a live drummer rather than from its own internal clocking? What potential pitfalls and hazards are involved? I have some thoughts already but rather than throwing them into the mix, I'd like to hear a clean-paged take on it from anyone who cares to chime in. Thanks in advance!