AT&T 6300 Programmer's Manual page 402

PLAY(n)
Function
Syntax
dummy
Remarks
Example
7-246
Returns the number of notes remaining in the
music background buffer.
PLAY (dummy)
is a dummy argument. Any value may be supplied.
If the program is running in Music
Foreground mode, PLAY(n) returns
o.
If the program is running in Music
Background mode, PLAY(n) returns the
number of notes currently in the Music
Background buffer. The maximum value that
PLAY(n) may return is 32.
IF PLAY(O)
=
6 GOTO 500