I think there's a bit of a special meaning between the mu- -use bit, which turns into the french opera piece. This is purely speculation, but to me, I get the feel of going into a dreamlike crescendo between the word "Muse." Matthew begins by singing the first syllable, trails off and the song swells into an imaginatively grandioso opera solo, complete with dramatic piano and backup chorus.
Then, as if falling out of a dream, the song returns with the end syllable "use."
It is like he is recalling the muse mid-sentence, and a fantastic image of her plays through his mind, and he returns to his senses (the rest of the song). The dreamlike sequence is obviously very fantastic and classic, much like a romantic dream (or like how things play out in a romantic opera), where the rest of the song is very upbeat and modern like the real world. Perhaps the dreamlike sequence is what he wishes to have played out to her, what he wants to convey: something beautiful and utterly romantic. But like he says when it comes to the modern part, he cannot find the words to say.
This was what I had playing in my head when I first heard it. It makes much more sense now that fanofmuse has given such a delightful background on the french stanza. What I imagined may not be true at all to the real context of the song, but it's still very fitting to imagine when listening to the song!