DG has put together a very smart reissue here. "Concerto grosso 1" and "Quasi una sonata" for violin and chamber orchestra were originally released in 1989. "Concerto grosso 5" has been rescued from its original 1993 release back-to-back with a Glass piece, and is now united with the other Kremer performances of Schnittke. The entire disc is a showcase for Gidon Kremer, who was Schnittke's friend and champion. Dohnanyi and the Vienna Philharmonic are amazing on "5", clearly outshining Schiff and the Chamber Orchestra of Europe, which perform with Kremer on the 1989 recordings. If you enjoy this music as much as I do, you should not miss Schnittke's violin concertos, played by Kremer (on Teldec) and his string quartets, played by Kronos (on Nonesuch) -- see my reviews of both. And don't miss Gubaidulina either -- DG 20/21 has recently released works for viola with Bashmet, and reissued OFFERTORIUM with Kremer -- see my review.
Schnittke called the 1977 piece an example of "polystylism," and sure enough there are elements of baroque and quotes from various composers, as well as a brief tango, but these are resolutely dissonant, modern works -- don't be misled into thinking otherwise. The ECM-esque cover photo is a great touch, credit to the DG 20/21 team.