In MMD 990913 Allan Merralls wrote about magnetic recording.

I am not sure if the Germans used a rotating magnetic head on their
audio recorders.  The only early application of rotating heads to
conventional audio recorders was for varying the length of recording
without changing the pitch (or vice versa!).  I doubt if the early
German recorders had this refinement.

Ampex developed the first really practical video recorder in 1956.
This used 4 heads on a drum scanning almost vertical tracks on 2 inch
wide tape.  The reason for rotating heads was to give a very high
head-to-tape speed at a sensible linear tape speed.  Needed in order to
record the very high frequencies in a video signal. I believe much of
the work on the video heads was done by Ray Dolby who went on to become
a household name.

In the late 1950s Ampex and others developed helical scan video
recording where the head(s) write tracks at a shallow angle with
respect to the motion of the tape.  All(?) modern video recording
formats and some data and audio systems such as DAT use helical
scanning.

Jeffrey Borinsky

 [ While I was working at the University of Illinois School of Music
 [ (as a computer consultant, not a musician or composer), I recall
 [ reading about an audio recorder that had a rotating head that
 [ made it possible to change playback speed without altering
 [ pitch, or conversely change pitch without altering playback
 [ speed.  This special effect came with a price -- a sort of
 [ burbling distortion in the playback, but it was adequate for
 [ compressing speech for "books on tape" and the like.  I never
 [ saw a drawing for this and don't know if it would play standard
 [ linearly recorded tapes or if it had to be used on tapes it
 [ made.  Does anyone know about this device ?  Thanks.  --Jody