By doubling up on the shelves used to house my CD collection, I somehow managed to double the shelf space available for my piano scores, which I'm currently in the process of dividing into areas of piano methods, solo piano scores, and chamber music/sonatas/concertos and then properly alphabetizing. Not done yet.
One of the great items I own but haven't located for years I've just found--a photocopy of Philip Cranmer's long out-of-print text The Technique of Accompaniment, which can be found in numerous libraries in the United States and a handful of libraries in Canada, but which I have still never located in the flesh, so to speak..
Here is an example from the first chapter, “Attitude of Mind”:
 Philip Cranmer, The Technique of Accompaniment (London: Dennis Dobson, 1970) 8-9
…How can we carry out any of them [our duties] if our attitude is one of inferiority and subservience to the music and our partner? We may quite rightly feel modest and humble beforehand, but if we are to interpret the music artistically these feelings of inadequacy must disappear as soon as we sit down to play. I have never yet seen the direction con discrezione on a piece of music.This subservient attitude can often be observed when the performers come on to the platform. A discreet accompaniment is predictable when one sees—floundering somewhat in the wake of a proud battleship of a soprano, weighed down by three Handel oratorios and four volumes of Lieder, so that his gaze can rise no higher than his boots—an insignificant little person who sidles on to the platform and hurries to his stool without even a glance at the audience, much less an acknowledgement of their greeting. He looks hand-dog at his mistress (I use the term in its animal sense), waiting for an imperious nod from her that will send him on his discreet journey through the first Purcell song (with which all the best singers begin their recitals)...
...To be sure, the assertive accompanist is just as bad. It is not so much that he plays far too loudly (though that is bad enough). Far worse is that he tries to take charge throughout, hogging the rallentandi, over-emphasising what should be only an echoing phrase, and so on. His approach is very much that of the selfish motorist who would like all other to be clared off the road. I have heard the opening chord of John Ireland's Sea Fever played as if it were the beginning of a piano concerto.