Beginning in the 1950s, popular music was revolutionized by the electrification of musical instruments, which has enabled musicians to play with increased volume. Because individual musicians can play with increased volume, the average number of musicians per band has decreased. Nevertheless, electrification has increased rather than decreased the overall number of musicians who play popular music professionally. Which one of the following is most strongly supported by the statements above, if those statements are true? ['The number of amateur musicians who play popular music has decreased.', 'Many professional musicians play in more than one band.', 'The number of professional musicians in some bands has increased.', 'The total number of professional bands has increased as a result of electrification.']