Derrida argues in defining presence that there is no meaning that exists outside of a text (I'm trying to skirt the signifier/signified issue associated with this). The rest of the phrase quoted argues that this cannot be the case, that there are certain outside factors that influence how the voice/body in singing are perceived by the listening audience.

In other words, there are meanings outside of the "text" (the singing); Derrida's conclusions are wrong.