Got the example working!

First found event parameters, how to modify them, and the setting in
FMOD for it to work in-engine.

examples/hello-fmod.rs

@@ -28,11 +28,47 @@ struct MyMusicPlayer;
 fn startup(mut commands: Commands, studio: Res<FmodStudio>) {
     let event_description = studio.0.get_event("event:/Martian Chess").unwrap();
 
+    studio
+        .0
+        .get_bank_list(10)
+        .expect("List banks")
+        .iter()
+        .for_each(|bank| {
+            info!("Bank: {:?}", bank.get_path().expect("Get bank path"));
+            bank.get_event_list(100)
+                .iter()
+                .flat_map(|events| events.iter())
+                .for_each(|event| {
+                    info!("Event path: {:?}", event.get_path());
+                    info!(
+                        "Event parameter description {:?}",
+                        event.get_parameter_description_by_name("Game State")
+                    );
+                });
+        });
+
     commands
         .spawn(MyMusicPlayer)
         .insert(AudioSource::new(event_description));
 }
 
 fn play_music(mut audio_sources: Query<&AudioSource, With<MyMusicPlayer>>) {
-    audio_sources.single_mut().play();
+    if let Ok(audio_source) = audio_sources.get_single_mut() {
+        audio_source.play();
+
+        info!(
+            "Parameter by name: {:?}",
+            audio_source
+                .event_instance
+                .get_parameter_by_name("Game State")
+                .expect("Get parameter")
+        );
+        match audio_source
+            .event_instance
+            .set_parameter_by_name("Game State", 5.0, true)
+        {
+            Ok(_) => (),
+            Err(e) => warn!("Error: {:?}", e),
+        };
+    }
 }