The bass guitar is a stringed instrument played primarily with the fingers or thumb, by plucking, slapping, popping, strumming, tapping, thumping, or picking. The bass guitar is similar in appearance and construction to a standard guitar, but with a longer neck and scale length, and four to six strings.
Bass guitar lock in with (especially) the bass drum and help link the main beat, the main pulse, of the music from the ‘dry’ sound of the drum to the ‘warmer’ sound of the harmony and melody content of the music.
Here’s a clip of a bass player playing the theme sound of Mario game.