Microphones; loudspeakers; sub-woofers; headphones; earphones; portable media players; audio amplifiers; audio interfaces; audio mixers; audio signal processors; audio-video receivers; electric and electronic effects units for musical instruments; amplifiers for musical instruments; wireless audio signal transmitters; car stereos; downloadable computer software; downloadable computer software for playing music; downloadable computer software for controlling audio apparatus; electronic publication featuring musical scores and sheet music; downloadable electronic music files provided from a computer network.