I wrote about these when in my article about the Notturno. Schubert wrote these in the last year of his life, and apart from the Notturno and an equally unfinished youth piece called Sonatensatz it is all he wrote for this particular instrumentation. I guess he made up for that by the sheer length of both compositions: they’re both about ten minutes longer than was common for pieces like this.
The second is the best known, especially the second movement of that piece made it in many movies and series. It also enjoys the dubious honour of being one of the few late pieces that Schubert heard on his deathbed.
My version of this record is from 1963 and in monaural sound. Even though at that time stereo was pretty much standard (since 1958). I think it was cheaper to release it this way. In 1973 the stereo version came out, belated. For comparison I’m now listening to the Beaux-Arts Trio’s version of 1986, which sounds way better.