You're being pedantic. The author was clearly not talking about media formats like CDs, which store music digitally as an implementation detail but are still a

You're being pedantic. The author was clearly not talking about media formats like CDs, which store music digitally as an implementation detail but are still a physical object that you buy just like records and tapes. It seems pretty clear that the author is talking about music whose primary form is purely digital, like MP3s that you could download on your computer and transfer to your iPod. Put another way: Anybody can tell you what a CD looks like — round, shiny, flat, about yea wide — but nobody knows what an MP3 looks like, because it is a purely digital format. The difference of physicality is the salient part here.