A repetiteur is essentially a piano player who helps singers and performers rehearse their music. However, there are many other terms that could be used to describe someone who provides musical accompaniment. A keyboardist, for example, would similarly play music for performers--but not necessarily during a rehearsal or practice session. A band member, on the other hand, might not possess the same level of musical expertise as a repetiteur, but could still accompany singers during a performance. Other synonyms for repetiteur might include accompanist, coach, or even conductor--depending on the context and specific musical needs at hand.