Tandy 600 Programmer's Reference Manual page 63

FUNCTION
D6h
-
Sound
Error
Tone
AX
BX
CX
DX
SP:
BP:
SI:
Dl:
IP:
FLG
CS
DS
SS
ES
XXXXXXXX
XXXXXXXX XXXXXXXX
Entry:
AH
=
D6h
(function
code)
BX
=
Tone channel
number
Exit
none
Function
D6h
is
used
to
sound an
error tone.
The
frequency
and
duration of
the tone are
set
via function
D7h.
58