There is lots of musical low bass in todays music. The fundamental frequency of the low B string on a 5 or 6 string bass is 31Hz in Concert Tuning with "A-440". If the group tunes down....well....they'll get below 31Hz on the bass.
Most modern electric jazz and reggae...and even heavy metal now use 5/6 string bass. Really bolsters the rhythm section if the bassist can play it.
So.....it's very common.