Wolfgang Amadeus Mozart: Sinfonia Concertante K. 364 [Lawrence Power & Nicola Benedetti] 

Wolfgang Amadeus Mozart (1756-1791): Sinfonia Concertante for Violin, Viola & Orchestra in E♭ major, K. 364 (1779)
00:11 - I. Allegro maestoso
13:31 - II. Andante
25:37 - III. Presto
Performers:
-Lawrence Power, viola (Antonio Brensi, Bologna, c.1590)
-Nicola Benedetti, violin/conductor
-Oxford Philharmonic Orchestra
//
"The magnificent Sinfonia concertante for violin, viola, and orchestra in E flat major, K. 364, is Mozart's only surviving complete work of this type, a genre that incorporates elements of both the symphony and concerto. Generally scored for two or more solo instruments and orchestra, the sinfonia concertante was particularly popular in Paris in the eighteenth century. It was there, in fact, that Mozart composed such a work in 1778 for four outstanding wind soloists from the Mannheim orchestra who were also then in the French capital; that work, however, is now known only in a spurious nineteenthth-century edition.
During this period Mozart also began two other works in the sinfonia concertante genre, one for violin and piano in D major (1778), and another for violin, viola and cello in A major, K. 320e (ca. 1779-1780), neither of which progressed beyond the first 130 or so measures before the composer set it aside. The present work may be a replacement for the aborted D major work. It was composed in Salzburg during the summer or fall of 1779, about the same time as that work. In both works, Mozart calls for a higher tuning than is usual for the viola; his purpose in so doing was undoubtedly to give the instrument a brighter sound to avoid being overshadowed by its more penetrating violin companion.
The soloists for whom the Sinfonia concertante was composed are not known, but they may have been Antonio Brunetti, the leader of the Salzburg court orchestra, and the violinist Joseph Hafender. The work is in three movements: Allegro maestoso, Andante and Rondo. The orchestra includes two oboes, two horns, an optional pair of bassoons, and strings. The work is notable for its warm expansiveness; the Andante is particularly delectable with its ravishing dialogue between the two soloists. The scoring is unusually full and rich; Mozart's frequent divisi writing for the violas produces textures that presage the sumptuous writing in Idomeneo, ré di Creta (1781), the opera seria composed for Munich less than a year later."
~Brian Robins [allmusic.com]