This is what I've found.
MusicCast Smart Home skills
Alexa, turn on the [Room Name].
Alexa, turn off the [Room Name].
Alexa, play in the [Room Name].
Alexa, pause in the [Room Name].
Alexa, resume in the [Room Name].
Alexa, stop the [Room Name].
Alexa, next in the [Room Name].
Alexa, previous in the [Room Name].
Alexa, set volume to [30] in the [RoomName].
Alexa, volume up in the [Room Name].
Alexa, volume down in the [Room Name].
Alexa, mute the [Room Name].
Alexa, unmute the [Room Name].
Alexa, switch input to [HDMI1] in the [Room Name].
Power on/off
Alexa, ask MusicCast to turn on the [Room Name].
Alexa, ask MusicCast to turn off the [Room Name].
Alexa, ask MusicCast to turn off all rooms.
Play/Pause/Stop
Alexa, ask MusicCast to play in the [Room Name].
Alexa, ask MusicCast to pause in the [Room Name].
Alexa, ask MusicCast to stop in the [Room Name].
Alexa, ask MusicCast to stop all rooms.
Play MusicCast Favorites/Playlists/Recents
Alexa, ask MusicCast to play [Favorite x] in the [Room Name].
Alexa, ask MusicCast to play [Playlist x] in the [Room Name].
Alexa, ask MusicCast to play Recents in the [Room Name].
Volume control
Alexa, ask MusicCast to set volume to [30] in the [Room Name].
Alexa, ask MusicCast to set group volume to [30] in the [Room Name].
Alexa, ask MusicCast to turn up the volume in the [Room Name].
Alexa, ask MusicCast to turn down the volume in the [Room Name].
Alexa, ask MusicCast to turn up the group volume in the [Room Name].
Alexa, ask MusicCast to turn down the group volume in the [Room Name].
Mute/Unmute
Alexa, ask MusicCast to mute the [Room Name].
Alexa, ask MusicCast to unmute the [Room Name].
Alexa, ask MusicCast to mute all rooms.
Next/Previous (Skip/Back)
Alexa, ask MusicCast to skip song in the [Room Name].
Alexa, ask MusicCast to play previous song in the [Room Name].
Repeat/Shuffle
Alexa, ask MusicCast to shuffle all songs in the [Room Name].
Alexa, ask MusicCast to turn shuffle off in the [Room Name].
Alexa, ask MusicCast to repeat one song in the [Room Name].
Alexa, ask MusicCast to repeat all songs in the [Room Name].
Alexa, ask MusicCast to turn off repeat in the [Room Name].
Input Selection
Alexa, ask MusicCast to switch input to [HDMI1] in the [Room Name].
Room Linking/Unlinking
Alexa, ask MusicCast to link the [Room Name] with the [Room Name].
Alexa, ask MusicCast to unlink the [Room Name].
Alexa, ask MusicCast to link the [Room Name] with all rooms.
Alexa, ask MusicCast to unlink all rooms.
Sleep Timer
Alexa, ask MusicCast to set sleep timer for [30, 60, 90, 120] minutes in the [Room Name].
Alexa, ask MusicCast to cancel the sleep timer in the [Room Name].
Now Playing
Alexa, ask MusicCast what's playing in the [Room Name].
Disklavier ENSPIRE Controls
Alexa, ask MusicCast to play the piano.
Alexa, ask MusicCast to stop the piano.
Alexa, ask MusicCast to skip the piano.
Alexa, ask MusicCast to play previous song on the piano.
Alexa, ask MusicCast to play [song name] on the piano.
Alexa, ask MusicCast to play the piano in Acoustic mode.
Alexa, ask MusicCast to play the piano in Quiet mode.
Alexa, ask MusicCast to turn up the volume on the piano.
Alexa, ask MusicCast to turn down the volume on the piano.
Alexa, ask MusicCast to turn on the piano.
Alexa, ask MusicCast to turn off the piano.