The May issue of Sunset magazine has a list of Top 10 Rafting Trips and #1 is a journey down the Colorado River with a string quartet. Yes a cellist actually carts her (or a rental) instrument down the Grand Canyon along with the violins and viola for rafters to enjoy the natural acoustics. A similar trip is chronicled in this 1998 article where the musicians battled against mosquitos along Utah’s Green River. One morning cello solo was called on account of bugs.