Simpson stated that String Quartets Nos. 4–6, which are on a much larger scale than Nos. 1–3, constituted "a close study of Beethoven's three Rasumovsky quartets, Op. 59; that is to say, the attempt to understand those great works resulted in, not a verbal analysis, but music". The three Simpson quartets offer, in his own idiom, "musical analogies" to the procedures of Beethoven's three quartets, but they can be performed without reference to the Beethoven and indeed without reference to each other.