Simplify the following text for a Grade 10 native English-speaking person.
Original: In the 1960s and 1970s some musicians took the frets off their bass guitars : taking the frets off a bass guitar changes the sound of the bass , particularly as the player slides their fingers along the strings . A bass guitar without frets is called a fretless bass guitar , and are favored by some bassists : for instance , Pino Palladino , whose performance on the fretless bass during the 1980s made him a highly desirable session player backing high profile musicians like Eric Clapton and David Gilmour .
Simplified: The first fretless bass guitar was made by Bill Wyman in 1961 when he converted an inexpensive Japanese fretted bass by removing the frets .