In addition to working on his own compositions, arranging the works of other composers was a constant in Mozart's life. In 1766, Johann Christian Bach was to publish his 'Six Sonatas for Pianoforte or Harpsichord Opus 5' in London. Wolfgang liked these so much that he arranged three sonatas from the collection as concertos for harpsichord. In these three concertos, the harpsichord part is practically identical to the original sonatas by J. Ch. Bach. Although the character of the manuscript suggests that the manuscript (which bears the hand of both Leopold and Wolfgang) could have been made between 1770 and 1772, it is likely that it is based on an earlier draft, close in time to the publication of the Opus 5 sonatas by Christian Bach. Whatever the case, Wolfgang probably planned these chamber concertos for later performances in small, private circles, both in Salzburg and on a new journey through Italy. In April 1764, Bach and the 8-year-old Mozart (!) performed together for the first time in London. The Mozart family's admiration for Johann Christian Bach lasted a lifetime.