diff --git a/src/518A0.c b/src/518A0.c
deleted file mode 100644
index cdfdf60..0000000
--- a/src/518A0.c
+++ /dev/null
@@ -1,3 +0,0 @@
-#include "global.h"
-
-#pragma GLOBAL_ASM("asm/us/nonmatchings/518A0/n_alMainBusPull.s")
diff --git a/src/libnaudio/n_mainbus.c b/src/libnaudio/n_mainbus.c
new file mode 100644
index 0000000..9bdcfb3
--- /dev/null
+++ b/src/libnaudio/n_mainbus.c
@@ -0,0 +1,76 @@
+/*====================================================================
+ *
+ * Copyright 1993, Silicon Graphics, Inc.
+ * All Rights Reserved.
+ *
+ * This is UNPUBLISHED PROPRIETARY SOURCE CODE of Silicon Graphics,
+ * Inc.; the contents of this file may not be disclosed to third
+ * parties, copied or duplicated in any form, in whole or in part,
+ * without the prior written permission of Silicon Graphics, Inc.
+ *
+ * RESTRICTED RIGHTS LEGEND:
+ * Use, duplication or disclosure by the Government is subject to
+ * restrictions as set forth in subdivision (c)(1)(ii) of the Rights
+ * in Technical Data and Computer Software clause at DFARS
+ * 252.227-7013, and/or in similar or successor clauses in the FAR,
+ * DOD or NASA FAR Supplement. Unpublished - rights reserved under the
+ * Copyright Laws of the United States.
+ *====================================================================*/
+
+#include "n_synthInternals.h"
+
+// This function appears to be different than the stock n_alMainBusPull.
+
+extern u8 D_800FC824;
+extern u8 D_80077D98;
+extern u8* D_800FC6D8;
+extern u32 D_800FD6F0;
+extern u8* D_800FCF28[];
+extern u32 D_800FCF30[];
+
+Acmd *n_alMainBusPull(s32 sampleOffset, Acmd *p) 
+{
+  Acmd        *ptr = p;
+    s32 i;
+
+  aClearBuffer(ptr++, N_AL_MAIN_L_OUT, N_AL_DIVIDED<<1);
+
+  ptr = (n_syn->mainBus->filter.handler)(sampleOffset,ptr);
+
+  aMix(ptr++, 0, 0x7fff, N_AL_AUX_L_OUT, N_AL_MAIN_L_OUT);
+  aMix(ptr++, 0, 0x7fff, N_AL_AUX_R_OUT, N_AL_MAIN_R_OUT);
+
+  // theres more code after?
+  if (D_800FC824 != 0) {
+      aClearBuffer(ptr++, 0x7C0, 0x2E0);
+      n_aLoadBuffer(ptr++, 0x170, 0x7C0, osVirtualToPhysical(&D_800FC6D8[D_800FD6F0 * 2]));
+      n_aLoadBuffer(ptr++, 0x170, 0x930, osVirtualToPhysical(&D_800FC6D8[D_800FD6F0 * 2]));
+
+      D_800FD6F0 += 0xB8;
+        if (D_800FD6F0 >= 0xB80) {
+            D_800FD6F0 = 0;
+        }
+      aMix(ptr++, 0, 0x7fff, N_AL_AUX_L_OUT, N_AL_MAIN_L_OUT);
+      aMix(ptr++, 0, 0x7fff, N_AL_AUX_R_OUT, N_AL_MAIN_R_OUT);
+      aClearBuffer(ptr++, 0x7C0, 0x2E0);
+  }
+
+  if (D_80077D98 != 0) {
+    for (i = 0; i < 2; i++) {
+          aClearBuffer(ptr++, 0x7C0, 0x2E0);
+          n_aLoadBuffer(ptr++, 0x170, 0x7C0, osVirtualToPhysical(&D_800FCF28[i][D_800FCF30[i] * 2]));
+          n_aLoadBuffer(ptr++, 0x170, 0x930, osVirtualToPhysical(&D_800FCF28[i][D_800FCF30[i] * 2]));
+
+        D_800FCF30[i] += 0xB8;
+        if (D_800FCF30[i] >= 0x8A0) {
+            D_800FCF30[i] = 0;
+        }
+        
+          aMix(ptr++, 0, 0x7fff, N_AL_AUX_L_OUT, N_AL_MAIN_L_OUT);
+          aMix(ptr++, 0, 0x7fff, N_AL_AUX_R_OUT, N_AL_MAIN_R_OUT);
+    }
+  }
+  
+  return ptr;
+}
+
diff --git a/yamls/us/rom.yaml b/yamls/us/rom.yaml
index 3eb73bb..6f16db0 100644
--- a/yamls/us/rom.yaml
+++ b/yamls/us/rom.yaml
@@ -123,7 +123,7 @@
     - [0x51740, c]
     - [0x517A0, c] # yay0 audio decoder
     - [0x51850, c, libnaudio/n_save]
-    - [0x518A0, c] # this is n_alMainBusPull but the function appears to have changed.
+    - [0x518A0, c, libnaudio/n_mainbus]
     - [0x51B20, c, libnaudio/n_synsetvol]
 
     # libleo