Those in the know among our readers will be aware that wandering through the music world like a ghost is an extra measure at the famous opening of Bach’s Well-Tempered Clavier I. It goes by the name of ‘Schwencke measure’. The Henle Urtext edition of the work contains 35 measures; with the ‘Schwencke measure’ the piece has 36 measures. If the extra measure were actually to be included in the prelude – and that is to be discussed – it would have to be between measures 22 and 23:
Browsing the Internet a bit, we can confirm that indeed this fateful insertion is still causing confusion. Various editions are compared in discussion forums, sometimes featuring the measure, sometimes not. And many a one poses the legitimate question: ‘Bach or not Bach here?
Ever since the appearance of the ‘New Edition of All the Works’, the source situation for the Well-Tempered Clavier has been clearly explained. The most important source for the music text is the autograph where at various stages Bach himself entered corrections. Consequently, it transmits the authoritative form. The autograph of the C-major Prelude consisting of 35 measures thus gets along without the ‘Schwencke measure’.
Bach’s autograph was, however, repeatedly copied. These copies then served again as models for other copies so that an extensive network of manuscripts has been preserved; some of these go back to Bach’s autograph directly, some in a roundabout way. One of the copyists was the Hamburg music director Christian Friedrich Gottlieb Schwencke (1767–1822). He made a manuscript of the Well-Tempered Clavier I that can be traced back to the autograph only by way of several presently lost intermediate stages. Showing up for the first time in this copy of Schwencke’s is the measure that has become so notorious.
Whether Schwencke himself added the measure or whether it was already there in one of the lost models can no longer be determined. More important perhaps is the question of how this idea of lengthening the prelude could have come up at all. Is something missing in Bach’s autograph?
Well, the piece is almost entirely subdivided into regular groups of four measures each. Though only just. One more measure – and the regularity would be perfect! So Schwencke had the feeling that the three measures, 21–23, had to be expanded into four, especially since the harmonic progression from m. 22 is in effect abrupt and audacious after m. 23. Schwencke must have thought that inadvertently this measure had gone astray in transmission and so he added it in the music text. Nevertheless, there is no doubt that Bach intended the irregularity and compression of measures 21–23; the definiteness of the source situation is not to be shaken.
Hermann Keller writes in his little book about the Well-Tempered Clavier: ‘Schwencke was a sophisticated and well-informed musician who was probably not thinking of improving Bach’ (Hermann Keller, Das Wohltemperierte Klavier von Johann Sebastian Bach, Kassel, etc.: Bärenreiter, 1965, S. 40). But that obviously was just the case. The supposed improvement found its way into print in the Well-Tempered Clavier; the ‘Schwencke measure’ has gradually managed to worm its way into the transmission history.
It began in the Bonn publishing house of Simrock (1801 or 1802) with the edition whose editor was probably Schwencke himself. The measure also showed up in the Peters edition of 1837 by Carl Czerny. To be sure, in other editions of the 19th century the provenance of the phantom measure was at times put right. But the big success of the Czerny edition – which today is also available again through Internet portals such as the ‘Petrucci Music Library’ – ensured that the ‘Schwencke measure’ found wide distribution. Unhelpful in this connection was Charles Gounod’s Méditation ‘Ave Maria’. This perennial top-seller from the 1850s quoted the Bach prelude of the Czerny edition and saw to it that the ‘Schwencke measure’ was adopted into the collective cultural memory.
Thus, the ‘Schwencke measure’ stubbornly survives right up to our day. Our Urtext edition of the prelude clearly presents the facts:
The footnote asterisk between mm. 22 and 23 refers to the following comment:
In 1783, the copyist Schwencke added after M 22 a measure based on the bass note G, which was adopted by many editions. This supplementary measure is not authentic.
For this reason no one need be seriously on the lookout for the lost measure!