I wouldn't tow too often, but once in a while shouldn't hurt. A car would probably be too heavey though (if you are just pulling it out of a problem spot maybe, but otherwise no). A trailer with a piano should be okay (as long as it isn't more than 3000lbs) but don't expect great perfomance (or gas milage). I pulled a uhaul with some of my stuff from New Brunswick to Ontario this summer (about 15 hours) and didn't hurt anything, but my car didn't like it too much (and mine has the slightly more powerful 16 valve engine) it wouldn't go over 60 miles per hour (didn't want to go any faster towing anyway) and the gas milage was about double what it normally is.

Hope this helps