Opera and singing

Before a performance a singer singt sich ein, and the small word sich is what turns the verb into a warm-up. With the reflexive pronoun, the separable prefix ein- describes doing an activity until you are ready for it: sich einsingen for the voice, and sich einspielen for an orchestra loosening up before the first downbeat. Drop the pronoun and the verb takes an object and means something else: ein Lied einsingen is to record a song in the studio. So the question to put to any sentence is whether the singer is doing something to herself or to a piece of music. Either way the prefix splits off in the present, sie singt sich ein, and in the perfect ge slips between prefix and stem while the auxiliary stays haben: sie hat sich eingesungen. The rest of the list belongs to the score, the pit and the stage door.