They sound "soft" sorta like a uke, but not as high pitched. They weren't used to sing along with -- that hadn't been invented yet! Only 5 notes to the pentatonic scale, but no sequence of notes you pluck ever sounds bad together. They were used as background music at feasts, and also by storytellers/bards to help them remember where they were when reciting long stories and sagas, as well a teaching far-flung people history, current events, and the rules of 'polite society'.