| You can work out the melody line to anything -- just cause it's bass doesn't mean a melody line can't sound cool.
And a great way to get a heap of great sheet music is to beg, borrow or steal a church hymnal. Used book stores often have one or two lying around for pretty cheap if you don't have a church connection. A lot of those hymns are arrangements of great classical compositions or traditional folk tunes and you can either take the melody line or extract the bass line off the piano score. My 11-year old son is learning sax and he and I did "be thou my vision" together for a school thing, he took melody and I took bass. It was a much more interesting line than pumping root notes on dance songs! That's not a solo, of course, but you get the idea. Chris Squire used to do a great solo of "Amazing Grace" (for that matter, seems like everyone does...). | 
