Not only can the Prius carry the upright bass, it can carry two passengers. Beside the front seat passenger, there is actually plenty of room in the back seat for a passenger. The bass takes up about have of the back seat and the cargo area. In fact, we took a summer road trip to take my son and his bass a to jazz camp in
My two boys often use the Prius to carry themselves and music gear to their jazz gigs around town. They carry the upright bass, a couple of amps, a guitar, music stands and other miscellaneous equipment. At one gig when they were unloading, a bystander was amazed at all the gear they carried. He said to them “you got all that in a Prius?”.
The Prius has a deceptively roomy interior for a compact car. The rear seat leg room in the Prius is as good as in most full size cars. It has equivalent rear leg room to my Chevy Impala. The interior space in the Prius is much better than the typically compact car. The Prius is a few inches than most compacts which makes it feel much roomier.