diff --git a/src/itdelatrisu/opsu/audio/MusicController.java b/src/itdelatrisu/opsu/audio/MusicController.java
index cfe3bb60..2bd2dcce 100644
--- a/src/itdelatrisu/opsu/audio/MusicController.java
+++ b/src/itdelatrisu/opsu/audio/MusicController.java
@@ -257,6 +257,14 @@ public class MusicController {
 		return (trackExists() && player.setPosition(position / 1000f));
 	}
 
+	/**
+	 * Sets the music volume.
+	 * @param volume [0, 1]
+	 */
+	public static void setVolume(float volume) {
+		SoundStore.get().setMusicVolume(volume);
+	}
+
 	/**
 	 * Plays the theme song.
 	 */
diff --git a/src/itdelatrisu/opsu/states/MainMenu.java b/src/itdelatrisu/opsu/states/MainMenu.java
index 0ea2aa95..2da0d4b6 100644
--- a/src/itdelatrisu/opsu/states/MainMenu.java
+++ b/src/itdelatrisu/opsu/states/MainMenu.java
@@ -102,6 +102,11 @@ public class MainMenu extends BasicGameState {
 	 */
 	private float bgAlpha = 0f;
 
+	/**
+	 * Whether the theme song volume has been dimmed.
+	 */
+	private boolean volumeDimmed = false;
+
 	// game-related variables
 	private GameContainer container;
 	private StateBasedGame game;
@@ -249,6 +254,18 @@ public class MainMenu extends BasicGameState {
 		musicNext.hoverUpdate(delta, mouseX, mouseY);
 		musicPrevious.hoverUpdate(delta, mouseX, mouseY);
 
+		// window focus change: increase/decrease theme song volume
+		if (MusicController.isThemePlaying()) {
+			boolean hasFocus = container.hasFocus();
+			if (volumeDimmed == hasFocus) {
+				if (hasFocus)  // restored focus
+					MusicController.setVolume(Options.getMusicVolume());
+				else  // lost focus
+					MusicController.setVolume(Options.getMusicVolume() / 3f);
+				volumeDimmed = !hasFocus;
+			}
+		}
+
 		// fade in background
 		if (bgAlpha < 0.9f) {
 			bgAlpha += delta / 1000f;