What Jon said is all true. It is very much an ensemble cast, so no one really sing's very much, if you know what I mean. I guess you might say Sara Ramirez sings a lot (at least in the first act), but during the second act even she comes on stage and throws a tantrum at not having more solos.

I myself (having a strange and unexplainable fondness for David Hyde Peirce) was slightly disappointed at the time that DHP spent on stage, so I understand your worries. But no fear- just stick around for the second act (DHP finally gets a big solo, and Arthur opens his mouth a lot more too). You shouldn't be very disappointed, especially by second act. You will hear enough to Tim's voice, and if its not enough for your taste, well there's always the cast album (which, from what I hear, is to be released in February), which you can put on repeat. (Its worth it, in my humble "I'll by any cast recording at all" opinion, just for Curry's verse of "Always Look On the Bright Side of Life.") And I agree, Sueleen, that IS half the fun.
But now we have come almost to the end. One last step. And then, when I take power, they will be pulled down and ground into dirt for what they did to you. And what they did in so contemptuously underestimating me.