Claim: The first and last pieces on the album, After Bach, are Mehldau compositions, and between these two, Mehldau plays four preludes and one fugue from  Johann Sebastian Bach's, The Well-Tempered Clavier (a collection of six sets of preludes and fugues in all 24 major and minor keys, composed for solo keyboard).
Evidence: After Bach is a solo album by pianist Brad Mehldau. The first and last pieces on the album are Mehldau compositions. Between these two, Mehldau plays four preludes and one fugue from Bach's The Well-Tempered Clavier; each is followed by one of his own compositions that is an interpretation of the Bach piece. The Well-Tempered Clavier, BWV 846–893, is a collection of two sets of preludes and fugues in all 24 major and minor keys, composed for solo keyboard by Johann Sebastian Bach.