Regrettably both the Yamaha MDF-3 and Viscount RD-70 have been discontinued. The RD-70 has been supplanted by the RD-80, which is a module that also has audio. My guess is with the prevalence of software based sequencing, the market has shrunk to the point where units like this are not supportable. I had to procure an RD-70 for a current project and it took some doing to track one down.
This is a shame, as these units were, to my knowledge, the only widely manufactured, discrete, stand-alone MIDI data recorders around. If anyone has knowledgeof a comparable unit from another manufacturer, I would like to hear about it.
In retrospect, neither unit was completely perfect, but both did their jobs well. The MDF-3 was compact, had simple, intuitive controls, and a side-loading drive. The RD-70 was a half-rack mount unit with controls on the front. They shared a common medium for data files: 3.5" floppy disks.
I believe some of the control system manufacturers have their own sequencer units in development with plans to utilize solid state storage media for data storage.
Edward Odell
J.H. & C.S. Odell