We currently own an Alesis ADAT. In a recording session done about two years ago, an Alesis SR16 drum machine was used to record 4 tracks to the ADAT which were then bounced to 2 tracks and the remaining 6 tracks were filled with other instruments. We are now unhappy with the mix we achieved on the 2 drum tracks and would like to change or replace them. My partner has purchased a Roland VS 1680. We would like to transfer all eight tracks from the ADAT to the Roland. We would also like to change or replace the drum tracks by redoing them on the Roland. Once we have transferred the tracks from the ADAT to the Roland, our intent will be to sync a drum machine to the tracks on the Roland and replace the drum tracks. We have the following problem:

How do we sync the drum machine so that it starts exactly in time with the transferred tracks on the Roland? To complicate the matter further, we do not know the beats per minute the SR16 drum machine was programmed for during the recording made so long ago. How do we determine this?