While still at work on the Quartet in A minor, Beethoven began sketching ideas for the third and last of the Golitsïn quartets in May or June 1825. According to Karl Holz, ‘new ideas streamed from [his] inexhaustible fantasy’ and, partly as a result perhaps, the number of movements in each successive quartet rose inexorably from four in op. 127 to five in op. 132 (if the Alla marcia and the ensuing recitative are counted as one movement rather than two); six in op. 130 (with an alternative finale added later) to seven in op. 131, dropping back to four in op. 135. Ideas were sometimes moved from one quartet to another; for instance, the beautiful Alla danza tedesca, placed originally in the A minor Quartet, was moved at quite a late stage to the Quartet in B flat major, and replaced by the Alla marcia, together with its dramatic recitative. ‘Art demands of us that we shall not stand still’, Beethoven told Karl Holz, adding: ‘Thank God there is less lack of fantasy [in the quartets] than ever before.’

Far from ‘standing still’, Beethoven worked with intense concentration while supposedly convalescing in Baden that summer. He had completed most of the new quartet by August, and assured Karl Holz in a letter, dated 24 August 1825, that he hoped to complete the sixth and final movement by the end of the month. Two comments in the relevant sketchbook suggest that he wanted to complete the set of three Golitsïn quartets in an imposing manner: ‘the last quartet with a serious and weighty introduction’, he wrote; and a few pages later: ‘last movement of the quartet in B flat-Fugha’. He would not have forgotten that Prince Golitsïn had been responsible two years earlier for staging the world premiere in St Petersburg of the Missa Solemnis, with its own ‘serious and weighty introduction’ and magnificent fugues, and he clearly decided to treat the last of the Golitsïn quartets just as seriously. However, he became so absorbed when writing the fugal finale, the Grosse Fuge, that it took him four months to complete rather than the predicted week or two; by late December it had grown to a massive 741 bars, 98 bars longer than the other five movements combined.