You can purchase Euphonium Unbound: Soaring or Euphonium Unbound: Winding from your Realm Depot: Riches of the Realm.
Tip #2
Open Editing Mode to place Euphonium Unbound: Winding indoors or Euphonium Unbound: Soaring outdoors.
Tip #3
Interact with Euphonium Unbound: Soaring or Euphonium Unbound: Winding to open the Realm's music menu, where you can then consume Radiant Spincrystals to unlock the corresponding tunes.
aka I'm too smart and cool to check it myself on the net, or use a calculator like genshin aspirine...