Casta-Mutes

Casta-Mutes are an Instrument Pouch item in Xenoblade Chronicles 2. They can be purchased from Nalinali at Strummer Instruments in the Argentum Bazaar in Goldmouth, Argentum Trade Guild. Completing the Merc Mission New Sounds is required to unlock this pouch item.

Trivia

 * They are most likely the in-universe equivalent of castanets.