diff --git a/ravi/CHANGES b/ravi/CHANGES
index 47ecf26..a6ef7f7 100644
--- a/ravi/CHANGES
+++ b/ravi/CHANGES
@@ -1,3 +1,10 @@
+November 1, 2021
+   - Merged version 0.5.4 of the original driver:
+
+     June 16, 2005 - BETA 0.5.4
+        - Turn off channels when their current instruments don't have a GM map
+          instead of defaulting to piano.
+
 October 31, 2021
    - A proper fix for 8086/80186 compatiblity, thanks to Jim Leonard.
    - Renamed the driver to "s2p.drv"
diff --git a/ravi/s2p.asm b/ravi/s2p.asm
index 30b0bf2..596d43a 100644
--- a/ravi/s2p.asm
+++ b/ravi/s2p.asm
@@ -5,13 +5,13 @@
 ; GM on MPU-401 driver for SCI0
 ; plays the MT-32 channels using Rickard's MIDI Mapping Magic
 ;    (see http://freesci.linuxgames.com)
-; assembles with NASM (see http://sourceforge.net/projects/nasm/):
+; assembles with NASM (see http://nasm.sourceforge.net):
 ;    nasm s2p.asm -o s2p.drv -f bin
 
-; Copyright (c) 1999, 2000, 2002, 2003 by
+; Copyright (c) 1999, 2000, 2002, 2003, 2005 by
 ;    Rickard Lind
 ;    Christoph Reichenbach
-;    Ravi Iyengar [ravi.i@softhome.net]
+;    Ravi Iyengar [ravi.i@rarefied.org]
 ;    Andy Hefner
 ;
 ; This program is free software; you can redistribute it and/or
@@ -115,6 +115,7 @@ pssndreset:    db 0          ; boolean describing whether PauseSound should rese
 seekto:        dw 0          ; the end point for SeekSound
 seekcue:       dw 0          ; the desired sound cue at the end of SeekSound
 globalvol:     dw 60         ; global volume on a scale of 0 to 63
+muteflags:     dw 0          ; bit flag for each channel used to mute channels that have no GM instrument
 
 MIDI_mapping:   times 128 db 0, 0, 0, 0, 0, 0, 0, 0
 end_of_MIDI_mapping:         ; used in ending loop conditions
@@ -175,6 +176,13 @@ ExportTable:
         pop     ax
 %endmacro
 
+%macro __setne 1
+        mov %1, 0
+        je %%skip
+        mov %1, 1
+%%skip:
+%endmacro
+
 ; DriverInterface
 ; Saves registers and calls export
 ; Entry: bp = export number
@@ -321,7 +329,7 @@ LoadSound:
    mov word [cs:pssndreset], 0  ; PauseSound does not reset by default
    mov byte [cs:fadeticks], 0   ; there is no fade in progress
    mov byte [cs:playstate], PLAYING ; we're playing this sound now
-   
+
    mov cx, word [si+SND_VOLUME]
    shl cx, 1
    shl cx, 1                 ; we use a range of 0-63 for internal global volume
@@ -581,11 +589,20 @@ StopNote:
 
 PlayNote:
    cmp byte [cs:playstate], PLAYING
-   je play_note
+   je check_mute
 
    add di, 2                 ; we're just seeking, don't play anything
    ret
 
+   check_mute:               ; check the channel mute flag
+   mov ax, 1
+   shl ax, cl                ; cl = channel
+   test word [cs:muteflags], ax
+   jz play_note
+
+   add di, 2                 ; skip over parameters
+   ret                       ; return without playing because the mute flag is set
+
    play_note:
    mov al, dl
    call mpu_output
@@ -629,7 +646,7 @@ ControlChange:
    pop bx
    je allow_cc
    ret                       ; ignore disallowed CCs
-   
+
    allow_cc:
    mov al, dl
    call mpu_output
@@ -671,13 +688,31 @@ PatchChange:
    test cl, 128
    jz do_patch_change
 
-   mov cl, 0                 ; we didn't find a mapped instrument, default to piano
+   mov al, dl
+   and al, 0x0F              ; al = channel
+   cmp al, 9                 ; see if this is the percussion channel
+   __setne al                ; mute this channel unless it's the percussion channel
+   jmp set_channel_mute
 
-   do_patch_change:
+   do_patch_change:          ; send the translated patch change to the mpu
    mov al, dl
    call mpu_output
    mov al, cl
    call mpu_output
+   mov al, 0                 ; make sure the channel isn't muted
+
+   set_channel_mute:
+   mov cl, dl                ; dl is still the status
+   and cl, 0x0F              ; cl = channel
+   mov bx, 1
+   shl bx, cl
+   not bx
+   and word [cs:muteflags], bx ; clear the mute flag for the channel
+   xor bx, bx
+   mov bl, al
+   shl bx, cl
+   or word [cs:muteflags], bx ; set the mute flag for the channel if al is set
+
    ret
 
 
diff --git a/ravi/s2p.drv b/ravi/s2p.drv
index 8053065..3d63698 100644
Binary files a/ravi/s2p.drv and b/ravi/s2p.drv differ
diff --git a/ravi/s2p.txt b/ravi/s2p.txt
index a4dcdcc..f3c62ff 100644
--- a/ravi/s2p.txt
+++ b/ravi/s2p.txt
@@ -9,14 +9,14 @@ The original documentation follows.
 ----------------------------------------------------------------------
 
 gm
-BETA 0.5.3
-Septermber 9, 2003
-Ravi I. [ravi.i@softhome.net]
+BETA 0.5.4
+Jun 16, 2005
+Ravi I. [ravi.i@rarefied.org]
 
 The gm driver is a General MIDI sound driver for Sierra's SCI0 games. This
 covers games like Conquests of Camelot, Space Quest III, most copies of
 King's Quest IV, Leisure Suit Larry III, and so on. The latest version of
-this driver is available from http://www4.ncsu.edu/~rniyenga/sci.
+this driver is available from http://www.rarefied.org/sci/.
 
 The driver is licensed under the GNU GPL with specific permission for linking
 with Sierra's SCI0 interpreter. Full details are available in the file
@@ -25,16 +25,16 @@ LICENSE. Source is available in the file gm.asm.
 Thanks to Rickard Lind and Christoph Reichenbach of the FreeSCI team (see
 http://freesci.linuxgames.com). Rickard wrote the patch mapping code in the
 file midi.c, which is copyrighted by him and Christoph. The code was
-translated into assembly for inclusion into this driver. Additionally,
-instead of muting the channel, the driver defaults to piano when an
-instrument could not be mapped.
+translated into assembly for inclusion into this driver.
 
 Contributors:
+   Rickard Lind
    Ravi Iyengar
    Andy Hefner
+   Christoph Reichenbach
 
 The driver also includes framework code. The framework driver is available
-from http://www4.ncsu.edu/~rniyenga/sci/.
+from http://www.rarefied.org/sci/.
 
 CAVEATS: This is an BETA version of the driver. Please feel free to report any
 bugs. To be especially helpful, include a patch.