For the OP, woodenspoon and others, there are masses of Cruise firms these days, Ocean and River, most of them desperate for customers!
My inbox has for many months had even the luxury end firms making increased offers to get 'bums on seats', or into cabins in this case. (And yes, Saga does offer that car ride for you, but if you compare their cost, you'll see how it's "included"?!).
In addition to Riviera, Viking, Titan, etc, there's Emerald, Avalon, AMA, Scenic, A-Rosa, and quite a few more. They will all to some extent depend on a guide -- IF you choose a ship's tour! - but the onboard experience should be pretty good on them all. Mind you, that "piped music" reference was a bit disturbing!
We've done lots of Sea cruises, and have learned to AVOID ship's tours in general (in just a few locations, the destination is too tricky to arrange yourself, so they are a necessary - and almost always overly expensive! - evil). River cruises are usually stopping in towns and cities, so it's relatively easy to do your own thing? If certain tours are included, on a given trip, well fair enough, go with the flow -- but any group tour or coach trip can have drawbacks like commentary, or someone loud you get stuck near?
Masses of research is out there, on an abundance of blogs and forums.