[1F 06] = Enable music changes caused by crossing sector boundaries.

C1/81F3: C9 06 00     CMP #$0006
C1/81F6: D0 03        BNE $81FB
C1/81F8: 4C 46 84     JMP $8446

C1/8446: A9 01 00     LDA #$0001
C1/8449: 22 45 FD C4  JSR $C4FD45

C4/FD45: C2 31        REP #$31
C4/FD47: 8D 49 B5     STA $B549
C4/FD4A: 6B           RTL 

C1/844D: 4C 68 86     JMP $8668

C1/8668: A9 00 00     LDA #$0000
C1/866B: 2B           PLD 
C1/866C: 60           RTS