While fretless basses are common with jazz and jazz fusion , bassists from other genres use fretless basses , such as metal bassist Steve DiGiorgio and Colin Edwin of modern\/progressive rock band ( Porcupine Tree ) . While fretless basses are often associated with jazz and jazz fusion , bassists from other genres use fretless basses , such as metal bassist Steve DiGiorgio and Colin Edwin of modern\/progressive rock band Porcupine Tree .