Explosion_Snd ($F92E)

This routine appears to generate some type of an explosion sound, dependent upon the 4 bytes which are pointed to by the U register. You will probably need to call Do_Sound for this to do anything. The format of the 4-byte block is:

1)

Bits 0-2 = ? Stored in $C85D
Bits 3-5 = ? Stored in $C853
Bits 6-7 = 0
Bits 0-2 and 3-5 are ORed and stored in bits 0-2 of
$C854

2)

<0 = ? Something to do with register 6
=0 = ?
>0 = ?

3)

<0 = ?
=0 = ?
>0 = ?

4)

Speed? Higher values = lower duration?

ENTRY:

DP = $C8

U-reg points to 4-byte block of data if $C867 high bit set

EXIT:

D-reg, X-reg trashed

Source