HOW TO LISTEN
One aside before getting stuck in: the only way to listen to this music is actively, and active listening is something which is taught less and less, leaving listeners to develop their own approaches. Thankfully, it is not difficult to acquire some good habits – I have 4 which work for me so I mention them here in case they are helpful.
Be prepared: Know what you are dealing with: what, when, why, where… You don’t want to be weighed down with info, but knowing nothing puts you at a disadvantage.
Repetition: listen to unfamiliar music over and over again until you find yourself humming along or anticipating favourite moments. Hey – you HAVE favourite moments. You also start to feel the bones beneath the surface, the ebb and flow of the piece. The only health warning is: listen to more than one recording to ensure that your view of the piece is not overly influenced by a single interpretation.
Compare: There is nothing like contrast to sharpen your ears. Anything works which offers a point of connection. With Op 127 you could find other quartets written in the early 1820s (Schubert?) or an utterly different quartet (Shostakovich?) or – the answer to health warning above – find very different performances: one from the 1950s, one by a young quartet, one by an acclaimed ensemble, a Viennese, French, American performance…. YouTube is a great source of rarities.
Change focus: now and then, set yourself a goal for a particular listen. Focus on the bassline, perhaps; or on how many kinds of texture are deployed; or how speed fluctuates – anything you find interesting.