String quartets op.20 No.4, op.64 No.5, op.76 No.1 and op.103 are chamber music works by Joseph Haydn, composed between approximately 1772 and 1797. They illustrate Classical-era quartet writing through balanced conversational interplay among the four instruments, clarity of sonata forms and inventive harmonic and motivic development, and they document key stages in Haydn's shaping of the string quartet as a genre that influenced later composers.
