AUDIE CORNISH, HOST:
The top-selling music artists of 2016 is not who you'd expect. If you looked at the most popular songs today, it's not Drake. He's runner-up.
(SOUNDBITE OF SONG, "HOTLINE BLING")
DRAKE: (Singing) You used to call me on my cell phone late night when you need my love - call me on my cell phone...
CORNISH: And it's not Adele. She's won 10 Grammys.
(SOUNDBITE OF SONG, "HELLO")
ADELE: (Singing) Hello from the other side.
ROBERT SIEGEL, HOST:
It is Wolfgang Amadeus Mozart.
(SOUNDBITE OF PERFORMANCE OF MOZART'S "EINE KLEINE NACHTMUSIK")
SIEGEL: That's right - Mozart.
(SOUNDBITE OF PERFORMANCE OF MOZART'S "EINE KLEINE NACHTMUSIK")
SIEGEL: And he became this year's top seller on the Billboard chart through another musical relic, the compact disc. He sold 1 and a quarter million CDs in just five weeks.
CORNISH: Here's how it happened. In October, the Universal Music Group released a box set for the 225th anniversary of Mozart's death. Quartz reporter Amy Wang says each disc in the box set counts as one CD sold.
AMY WANG: So because each box set contains 200 discs, each person who bought it technically bought 200 CDs all at once.
CORNISH: Wang says it may sound like just a technicality, but the fact that Mozart beat out artists like Drake and Adele should make the music industry worried.
WANG: And it's very telling of the fact that the music industry is struggling to even sell CDs in the first place if an artist from the 18th century is coming out to overtake today's best artists.
SIEGEL: So who's buying a 200-disc Mozart boxed set anyway?
WANG: Younger listeners are probably not the type to be in this category since most young people are used to this $10-a-month streaming buffet idea.
SIEGEL: And that raises another problem. Young people especially just aren't buying CDs.
WANG: The record industry has quite a few things to worry about at the moment, and one of them is how exactly to transition from the format of physical music to digital.
CORNISH: That's a challenge that will last into the New Year. 2016 belongs to Mozart.
(SOUNDBITE OF PERFORMANCE OF MOZART'S "SYMPHONY NO. 40 IN G MINOR") Transcript provided by NPR, Copyright NPR.