The Nouns of French Instruments

In the singular we have a simple sound. In the plural it's different. If we were talking about several people we'd say. Il l'eis. Aurelia is musical, right? We En jou desaix sofon et de la gitter. El et oceis por tiv. El féde le scallade. Che means to someone's place or to a particular place without mentioning the exact location. Nousif which means harmful or noxious would become... Nousif.