The facilities offered by the organ, with its several keyboards, for the delineation of these designs, rendered it particularly appropriate that they should be transcribed for that instrument. This Bach did. In addition to sixteen transcriptions for the harpsichord, he left us arrangements for the organ of three of Vivaldi's[78] concertos, and the first movement of a fourth.[79] They are arrangements, rather than integral reproductions; and if we take a certain interest in this transcription for the organ, by special methods, of works not originally intended for that instrument, it is an interest like that inspired by a well-made translation. [Footnote 78: P. viii, 1-4. Vivaldi was born toward the end of the seventeenth century; in 1713 he was appointed _maestro di cappella_ at _l'Ospitale della Pietà_, at Venice; later he was for some time in the service of the Landgrave of Hesse-Darmstadt. He died in 1743.] [Footnote 79: The title of this last transcription gives us a clue to its date; it reads as follows: "_Concerto dell'illustrissimo Principe Giovanni Ernesto Duca di Sassonia appropriato all'Organo a 2 clav. e pedale da Giovanni Sebastiano Bach_." So it must have been written before 1715, the date of the Duke's death. Bach was not the only one to make these transcriptions; Mattheson tells us (_Das beschützte Orchester_): "Compositions of this order (_concerti grossi_, _sinfonie in specie_, overtures) may also be played upon a polyphonic instrument, for instance upon the organ or harpsichord; a few years ago the celebrated S. de Graue, the blind organist of the new Dunes Church in Amsterdam, played from memory and with remarkable clearness in my presence, upon the excellent organ in his church, the latest Italian sonatas and concertos in three and four parts."] Possibly Bach regarded it in another light; for him it may have been a means of penetrating to the core of such compositions, of analyzing their inherent qualities. We now see him quite preoccupied with this three-movement form; take, for instance, the Toccata in _C_ major.[80] [Footnote 80: P. iii, 8. B.-G. xv, p. 253.] The Prelude itself is subdivided. First we find an introduction,[81] free in style; then an Allegro, built, as is very important to notice, upon two different and well-defined themes.[82]