These were recorded over 30 years ago. As I said, I can’t remember any need for this though the tapes were the keyboards for the band with a click track for the drummer. I’ll try more tapes but maybe I was thinking we might use an outboard synth. I honestly don’t remember and the 644 is long gone.
"The 644 Midistudio ® is a 4-channel multitrack cassette
recorder, a 16 input mixing system with electronic
routing control, and a Ml DI Tape Synchronizer com-
bined into a single workstaion . It's the first Portastudio®
expressly designed to meet the challenge of the MIDI
revolution . Its mixing section is designed in a new
way to accommodate the greater number of line inputs
in a typical MIDI studio, up to 16 at once plus 4 effect
returns. Each main channel can access up to 4 effects
busses, so you can use a variety of different effects
(reverbs , de lays, choruses etc .) on different inputs. MIDI
Tape synchronization with Song Position Pointer (same
as that used by the T ASCAM MTS-30) is built in, so that
the capabi lities of MIDI sequencing can be blended with
the advantages of multitrack recording."