Though nothing like that to my knowledge has come out, we do have the Keller Quartet doing a wider range of quiet movements on the recent Cantante e tranquillo (ECM New Series 2324 B0021591-02). The performances and the selections stand out in a program that puts you in a profoundly tranquil frame of mind, reflective, inward.
The late Beethoven Quartets are here in slow movements from Quartets Nos. 16 and 13, we have string quartet arrangements of segments of Bach's "The Art of the Fugue," and then we have a number of modern works, a movement from Alfred Schnittke's "Piano Quintet," and excerpts from works by Ligeti, Kurtag, and Alexander Knaifel. Not all are quartets (there are also duos, trios, quintets) but all are deeply probing, meditative, absorbing, moody in the best ways.
The Keller Quartet has an exquisite sensitivity towards the music. That and the quality of the works make us take pause, listen, drift along with it all. It is an extraordinary program and I cannot recommend it strongly enough for when you are in a mood for reflection.