Mellotronists

<< I think it's a tape recording of a single sustained note slowed down
so much that the ultrasonic bias oscillator frequency is audible as
the high pitch.  The quivering effect on the high pitch would be the
wow and flutter of the tape. >>

that seems reasonable- bias frequencies were generally lower in those days, 
even on professional machines. has anybody seen a really good explanation of 
how bias works? I'll have to dig this out and have another listen, but 
there's a similar effect on "are you experienced?".

d./400nr1098 (not biased at all) and a small army of 1/4" machines.