Concert music is unique in that ensembles vary in size. Symphony orchestras can have more than 100 musicians, but there are much smaller ensembles, such as quartets. Therefore, it's these small groups that could be compared to other small, pop bands, although, it's often not only about one performer. Classical music has some great soloists, but their popularity cannot be compared to that of pop singers.
Another unique thing about concert music is that it's a niche market. You first need to find an audience that is willing to pay to listen to concert music. It is a very special, niche audience.
The other thing about classical music is that all orchestras share the same repertoire of internationally renowned composers, making it very hard to stand out in the digital landscape.
With all of these changes happening right now, it's very difficult for classical music groups to distinguish themselves on the Internet, to reach their audiences, and to get the royalties they are entitled to, yet get hardly any of.
Perhaps what is truly unique with concert music, compared to popular music, is that it is niche music, and reaching audiences is much harder than with other types of music.