Allegri Quartet, Bishop, Brymer
"Kegelstatt Trio & Stadler Quintet" (Vinyl)

Mozart's unusual instrumentation (piano, clarinet and viola) for his 'Kegelstatt' trio is a jewel for violists. Rarely did Mozart (who regularly intended to perform the viola parts himself) extend his writing beyond what the viola regards as comfortable. Of course he helped press these boundaries in his own way (the 'Sinfonia Concertante') but this particular work gives us a glimpse of Mozart's ideas of what the viola was capable of. Mozart wrote violin sonatas, but this is as close to pairing the viola directly with piano as we get.
It's a beautiful, whimsical piece. Borne of the same age as 'Marriage of Figaro' it demonstrates Mozart at the height of his composing power.
The 'Stadler' quintet I'm not familiar with - I'll listen to it when the record flips.

The recording and performances themselves are careful, if not cautious, and clean. The clarinet, by virtue of it's design, dominates the microphone a bit, but this could be expected in a live performance as well.