“Every concertgoer has wished at one time or another for a little guidance while listening to an unfamiliar piece of music — an experienced voice that could subtly whisper, ‘Here comes the second theme again,’ or, ‘That’s a bass clarinet making that rumble’ at the relevant moment. Now, thanks to wireless technology, that voice is available. Sotto voce, of course.” The hand-held Concert Companion was inspired by art-museum audio guides and operatic supertitles.