5 in A majorString Quartet No. 4 in C minorString Quartet No. Six String Quartets (1800), Opus 18String Quartet No. 1-6, Opus 18 are thought to demonstrate his total mastery of the classical string quartet as developed by Haydn and Mozart. 6 in B flat majorString Quartet No. 7 in F major, Opus 59, no. 1String Quartet No. If Haydn is today called the ‘father’ of the String Quartet, and Mozart took the form to new heights, then Beethoven – characteristically – took hold of it and completely transformed it. The five Late Quartets, written in the final years of his life, transcend anything he or anyone else had ever composed. 2 in G majorString Quartet No. The String Quartets Nos. Beethoven's String Quartets The sixteen quartets of Ludwig van Beethoven are highly acclaimed. 1 in F majorString Quartet No. 3 in D majorString Quartet No.