Hello It’s a piece packed with ideas, and the interweaving of the string parts is well crafted. I’m not sure what your level of experience is, although you mention that you want to improve your harmonic structure… I mention this because the piano part reveals a certain lack of experience in handling the instrument’s idiom. One point in particular: when you’re accompanying with block chords, it isn’t necessary to ‘fill’ the entire range. And especially in the lower register – the left hand from F on the fourth line downwards, more or less – avoid stacking thirds, as it all sounds very muddled. In the lower register, you need to open up the intervals, to at least a fifth. This is very evident from bar 23 onwards, with the ‘presto giocoso’. Writing for solo instruments in ensembles such as quartets, etc., is very difficult because, on the one hand, you have to maintain the independence of each instrument and keep the listener engaged with what it is doing, whilst, on the other hand, ensuring that the combination results in proper counterpoint and derived harmony. I believe that to begin developing a grasp of harmony (more or less exclusively), it is best to write for a polyphonic instrument (piano) or for piano and a solo instrument.