diff --git a/agb/src/sound/mixer/mixer.s b/agb/src/sound/mixer/mixer.s
index 33f59172..4af591e1 100644
--- a/agb/src/sound/mixer/mixer.s
+++ b/agb/src/sound/mixer/mixer.s
@@ -95,10 +95,12 @@ agb_arm_func agb_rs__mixer_add_stereo
     @ Arguments
     @ r0 - pointer to the data to be copied (u8 array)
     @ r1 - pointer to the sound buffer (i16 array which will alternate left and right channels, 32-bit aligned)
+    @ r2 - volume to play the sound at
     @
     @ The sound buffer must be SOUND_BUFFER_SIZE * 2 in size = 176 * 2
-    push {r4-r8}
+    push {r4-r9}
 
+    mov r9, r2
     ldr r5, =0x00000FFF
 
     ldr r8, =agb_rs__buffer_size
@@ -128,7 +130,7 @@ agb_arm_func agb_rs__mixer_add_stereo
     lsl r6, r6, #24        @ r6 = | R | 0 | 0 | 0 | drop everything except the right sample
     orr r6, r7, r6, asr #8 @ r6 = | 1 | R | 1 | L | now we have it perfectly set up
 
-    add r4, r4, r6, lsl #4  @ r4 += r6 << 4 (calculating both the left and right samples together)
+    mla r4, r6, r9, r4     @ r4 += r6 * r9 (calculating both the left and right samples together)
 
     str r4, [r1], #4         @ store the new value, and increment the pointer
 .endr
@@ -136,7 +138,7 @@ agb_arm_func agb_rs__mixer_add_stereo
     subs r8, r8, #4          @ loop counter
     bne 1b                   @ jump back if we're done with the loop
 
-    pop {r4-r8}
+    pop {r4-r9}
     bx lr
 
 agb_arm_end agb_rs__mixer_add_stereo
diff --git a/agb/src/sound/mixer/sw_mixer.rs b/agb/src/sound/mixer/sw_mixer.rs
index 676c0ed8..80b5b139 100644
--- a/agb/src/sound/mixer/sw_mixer.rs
+++ b/agb/src/sound/mixer/sw_mixer.rs
@@ -25,7 +25,11 @@ extern "C" {
         right_amount: Num<i16, 4>,
     );
 
-    fn agb_rs__mixer_add_stereo(sound_data: *const u8, sound_buffer: *mut Num<i16, 4>);
+    fn agb_rs__mixer_add_stereo(
+        sound_data: *const u8,
+        sound_buffer: *mut Num<i16, 4>,
+        volume: Num<i16, 4>,
+    );
 
     fn agb_rs__mixer_collapse(sound_buffer: *mut i8, input_buffer: *const Num<i16, 4>);
 }
@@ -447,6 +451,7 @@ impl MixerBuffer {
                     agb_rs__mixer_add_stereo(
                         channel.data.as_ptr().add(channel.pos.floor()),
                         buffer.as_mut_ptr(),
+                        channel.volume,
                     );
                 }
             } else {