The Mellotron Group

If any one is familiar with Roberts tape recorders, or Akai if not 
stateside, models 990, 997, and early 720 were half track capable 
machines.  A rotary switch on the heads gave you choices of 1/4 track 
left-stereo-right in 1/4 track mode and 2 track stere, or half track. 
These were introduced in 1962 and are tube (valve) driven. All machines 
had speeds of 3 3/4, 7 1/2, and 15 i.p.s. and although s/n and wow and 
flutter charachteristics were not as good as later machines, they were 
very impressive in their time.  One feature these machines included was 
switchable bias for recording speeds, basically a treble roll off for 
higher speed.  These were institutional work horses in their day and 
even today, I can still get belts, idlers, tubes, and still use mine 
quite a bit.  Doug