^ Yup, no tax for hand carried items.

As long as it will fit in the overhead, it is fine. I've flown with a guitar three times and they never hassle me about anything.

But with a bass, and possibly a hardcase, I doubt it will fit. There is hope though - I flew MAS on one of my flights back and they actually took my guitar (w/hardcase) and put it in a coat closet/wheelchair storage bay in 1st class (I was flying economy, btw). I don't know if this is the norm, but the steward guy was really nice and took it as soon as I boarded the plane, and later delivered it to me at the exit. I think this is called gate check-in or something to that effect - enquire with the airline to see if they provide this.

Please DON'T even think about checking it in, UNLESS you have a flightcase (which would probably cost about the same as the flight!!)