diff --git a/examples/noise_triangle_sfx.nes b/examples/noise_triangle_sfx.nes
index 00ed762..d96c03a 100644
Binary files a/examples/noise_triangle_sfx.nes and b/examples/noise_triangle_sfx.nes differ
diff --git a/src/assets/chr.rs b/src/assets/chr.rs
index cc95066..2e1c99c 100644
--- a/src/assets/chr.rs
+++ b/src/assets/chr.rs
@@ -92,7 +92,7 @@ pub fn png_to_nametable(path: &std::path::Path) -> Result<([u8; 960], [u8; 64]),
 
     // Attribute table: 8×8 bytes, each covering a 32×32 region made
     // up of four 16×16 quadrants. Each quadrant gets 2 bits
-    // (0..=3) packed into the byte as `TR<<6 | TL<<4 | BR<<2 | BL`
+    // (0..=3) packed into the byte as `BR<<6 | BL<<4 | TR<<2 | TL`
     // per the PPU's documented layout. The 15-row nametable only
     // half-fills the last attribute byte-row (rows 8..10 of the
     // bottom attribute byte are unused and stay at 0, matching the
diff --git a/src/codegen/ir_codegen.rs b/src/codegen/ir_codegen.rs
index 7b004cb..aa176fe 100644
--- a/src/codegen/ir_codegen.rs
+++ b/src/codegen/ir_codegen.rs
@@ -1407,10 +1407,15 @@ impl<'a> IrCodeGen<'a> {
         self.emit(STA, AM::Absolute(0x400A));
         self.emit(LDA, AM::Immediate(period_hi));
         self.emit(STA, AM::Absolute(0x400B));
-        // Enable pulse-1 + pulse-2 + triangle in the APU status
-        // register. We don't bother reading $4015 first — overwriting
-        // with $07 keeps all currently-used channels enabled.
-        self.emit(LDA, AM::Immediate(0x07));
+        // Enable all four tone channels in the APU status register.
+        // We always write $0F (pulse1+pulse2+triangle+noise) instead
+        // of just the channel we're triggering, because per-play
+        // writes use immediate values and a later noise play with
+        // $0B would otherwise silence an in-progress triangle note
+        // by clearing bit 2. Channels with no active envelope stay
+        // silent via the runtime's per-channel counter gating, so
+        // enabling them blindly is harmless.
+        self.emit(LDA, AM::Immediate(0x0F));
         self.emit(STA, AM::Absolute(0x4015));
         // Main-RAM envelope pointer.
         self.emit(LDA, AM::SymbolLo(label.to_string()));
@@ -1439,8 +1444,9 @@ impl<'a> IrCodeGen<'a> {
         // $400F: length counter load.
         self.emit(LDA, AM::Immediate(period_hi));
         self.emit(STA, AM::Absolute(0x400F));
-        // Enable pulse-1 + pulse-2 + noise channels.
-        self.emit(LDA, AM::Immediate(0x0B));
+        // Enable all four tone channels — see the equivalent write
+        // in `emit_play_triangle` for why $0F rather than $0B.
+        self.emit(LDA, AM::Immediate(0x0F));
         self.emit(STA, AM::Absolute(0x4015));
         // Main-RAM envelope pointer.
         self.emit(LDA, AM::SymbolLo(label.to_string()));
diff --git a/tests/emulator/goldens/noise_triangle_sfx.audio.hash b/tests/emulator/goldens/noise_triangle_sfx.audio.hash
index 5f988a9..5c09402 100644
--- a/tests/emulator/goldens/noise_triangle_sfx.audio.hash
+++ b/tests/emulator/goldens/noise_triangle_sfx.audio.hash
@@ -1 +1 @@
-a82b6ff5 132084
+8fd9f7d2 132084