Playing Music and Sound

Nu exposes a very simple audio API via the World module -

        /// Get the currently playing song, if any.
        static member getCurrentSongOpt world = ...
            
        /// Get the currently playing song's position or 0.0.
        static member getCurrentSongPosition world = ...

        /// Get the master volume.
        static member getMasterAudioVolume world = ...

        /// Get the master sound volume.
        static member getMasterSoundVolume world = ...

        /// Get the master song volume.
        static member getMasterSongVolume world = ...

        /// Set the master volume.
        static member setMasterAudioVolume volume world = ...

        /// Set the master sound volume.
        static member setMasterSoundVolume volume world = ...

        /// Set the master song volume.
        static member setMasterSongVolume volume world = ...

        /// Send a message to the audio system to play a song.
        static member playSong fadeInTime fadeOutTime startTime volume song world = ...

        /// Send a message to the audio system to play a sound.
        static member playSound volume sound world = ...

        /// Send a message to the audio system to fade out any current song.
        static member fadeOutSong fadeOutTime world = ...

        /// Send a message to the audio system to stop a song.
        static member stopSong world = ...

Since these functions are all side-effecting on the world, you will typically call them from your dispatcher's Command override.

However, you don't have to call the song playing functions manually if each screen has its own associated song (here, Assets.Gameplay.DeadBlazeSong) like BlazeVector does -

        override this.Content (_, _) =
            [...
             Content.screen<GameplayDispatcher> Simulants.Gameplay.Name (Dissolve (Constants.Dissolve.Default, Some Assets.Gameplay.DeadBlazeSong)) [] []
             ...]

The Content.screen function allows you to associate a particular song asset with the given screen such that it plays when that screen becomes actively, managing cross-fading and cross-screen song persistence for you.

When you wish to control the music on a particular screen yourself, you can simply pass None, then in a command hooked to the screen's Screen.IncomingStartEvent, call World.playSong yourself.