Im not a wiccan, so I'll answer you from druidry's perspective. According to the ancient druids' belifs, the entire world is made of vibrations or sound. So yes, music and sound in a broader sense, are not only important, but essencial.
In the case of a spell, in example, the words are important, but also intonation, strength, tone... so a spell casted and not properly pronounced, will not have the desired efects.
That is the reason of why most of knowledge of druids disappeared: it was forbidden (and impossible) to transcribe all these shades down.