diff --git a/src/MacLO.pi.bin b/src/MacLO.pi.bin
index ff7f326..2bdb471 100644
Binary files a/src/MacLO.pi.bin and b/src/MacLO.pi.bin differ
diff --git a/src/MacLO.pi.rsrc.bin b/src/MacLO.pi.rsrc.bin
index 99d58e0..d7b2249 100644
Binary files a/src/MacLO.pi.rsrc.bin and b/src/MacLO.pi.rsrc.bin differ
diff --git a/src/Sounds.c b/src/Sounds.c
index 00c2731..84f7003 100644
--- a/src/Sounds.c
+++ b/src/Sounds.c
@@ -1,9 +1,13 @@
 // Copyright (c) Jon Thysell <http://jonthysell.com>
 // Licensed under the MIT License.
 
+#include <GestaltEqu.h>
+
 #include "Sounds.h"
 
-#define ClickSndResID BaseResID
+#define SndBaseResId  8192
+
+#define ClickSndResID SndBaseResId
 #define RetrySndResID (ClickSndResID + 1)
 #define DoneSndResID  (RetrySndResID + 1)
 
@@ -12,9 +16,19 @@
 
 void Sounds_Init(Sounds *pSounds)
 {
-    pSounds->Enabled = DefaultEnabled;
+    OSErr err;
+    int32_t sysVersion;
     
-    SndNewChannel(&(pSounds->SndChannel), 0, 0, nil);
+    pSounds->Enabled = DefaultEnabled;
+    pSounds->SndChannel = nil;
+    
+    err = Gestalt(gestaltSystemVersion, &sysVersion);
+    if (err == noErr && sysVersion >= 0x0700)
+    {
+        // Only create a shared sound channel on System 7
+        // or above in order to cheaply support async sound
+        SndNewChannel(&(pSounds->SndChannel), 0, 0, nil);
+    }
     
     pSounds->ClickSnd = GetResource('snd ', ClickSndResID);
     if (pSounds->ClickSnd == nil)
@@ -39,7 +53,9 @@ void Sounds_PlayClickSnd(const Sounds *pSounds)
 {
     if (pSounds->Enabled)
     {
+        HLock(pSounds->ClickSnd);
         SndPlay(pSounds->SndChannel, pSounds->ClickSnd, PlaySoundsAsync);
+        HUnlock(pSounds->ClickSnd);
     }
 }
 
@@ -47,7 +63,9 @@ void Sounds_PlayRetrySnd(const Sounds *pSounds)
 {
     if (pSounds->Enabled)
     {
+        HLock(pSounds->RetrySnd);
         SndPlay(pSounds->SndChannel, pSounds->RetrySnd, PlaySoundsAsync);
+        HUnlock(pSounds->RetrySnd);
     }
 }
 
@@ -55,6 +73,8 @@ void Sounds_PlayDoneSnd(const Sounds *pSounds)
 {
     if (pSounds->Enabled)
     {
+        HLock(pSounds->DoneSnd);
         SndPlay(pSounds->SndChannel, pSounds->DoneSnd, PlaySoundsAsync);
+        HUnlock(pSounds->DoneSnd);
     }
 }