Beethoven's 7th string quartet, Opus 59, No.1 ("Razumovsky" 1) has always been one of my favorites. Composed at the height of his "heroic" phase, this quartet takes many chances and always lands on its feet. Despite the fact that it actually "offended" a few early performers, now it's one of the bedrocks of the string quartet repertoire. Here's the Juilliard Quartet in a performance from 1975.
Juilliard String Quartet:
Polling in Bavaria in 1975, at the beautiful baroque library of the former Augustinian Monastery to the south-west of Munich.
Robert Mann violino
Earl Carliss violino
Samuel Rhodes viola
Joel Krosnick violoncello
String Quartet 7 "Razumovsky", in F, Op.59 (1806) No 1
1.Allegro
2.Allegretto vivace e sempre scherzando (si bemolle maggiore)
3.Adagio molto e mesto (fa minore)
4.Allegro
Link
More about String Quartet 7 in a previous post HERE.
Here's a rough but interesting rehearsal extract of String Quartet 5, Opus 18, No.5 with an ensemble led by violin virtuoso Jascha Heifetz:
(Jascha Heifetz, Carol Sindell, Erick Friedman and Nathaniel Rosen)
Link