Music. David Owen wrote a very nice piece in the April 10, 2006 issue of the New Yorker about Muzak, the company that specializes in background music for retail establishments, office elevators, and on-hold entertainment. The company has reinvented itself with some success.
To my ear, however, the trend is away from a Muzak-type service and toward what Starbucks has done with Hear music. Traditionally, companies have spent far more time and effort developing a visual identity than an aural identity. That's beginning to change, as automobile manufacturers have discovered that rock n' roll sells cars, and retailers increasingly begin to develop and package "their" sound.
Brick-and-mortar record stores continue to experience the pain of disintermediation, while lifestyle retailers (coffee, clothing, etc.), begin to add CDs as a new line of merchandise. Interesting times.