Buying music is passe; nowadays it's all about renting. Billboard reports that sales of "album plus track equivalent albums" fell by 7.6 percent in 2013. (Among subcategories of both digital and physical media, only vinyl sales increased last year.) The new hot trends are monthly subscription services that let people rent unlimited music from large catalogs hosted in the cloud, as well as personalized radio services that make money by selling ads.

Both types of services seem to have a tough time making any money. Pandora has had negative net income for years. Spotify, the industry leader, has more than 6 million paying subscribers. However, it has lost more than $200 million since 2008, according an October estimate from PrivCo, a research firm that studies nonpublic firms, and the size of those losses has been ballooning. This dubious track record isn't stopping rap star and music producer Dr. Dre (real name, Andre Young) and Jimmy Iovine, the co-founder of Interscope Records. The duo has already created a company worth at least $1 billion by selling high-end headphones and speakers to the public. On Jan. 21 the pair plan to launch a new streaming service in the United States known as Beats Music.

I can't really tell why existing Spotify users would want to switch since, on the surface, Beats Music has basically the same set of features for the same price. (Beats boasts that its playlists are all curated by human experts and that it doesn't "present music as a database list," but Spotify also has human curators. It won't be possible to compare the quality of these rival services until Beats actually launches.)