and a G. Likewise, an octave line over a series of notes can begin or end ambiguously. Different solutions are given by different editors, and this is one manifestation of the improvisatory tradition of organ performance of the period. References External links Facsimile of the first 38 measures of J. S. Bach's autograph score in organ tablature of BWV 1121 Keyboard instruments Organs (music) de:Tabulatur#Tasteninstrumente