Vocal music
Reconstructions of Bach's vocal music are often based on surviving lyrics, such as librettos, which show similarities with those of extant music, so that the variant text can be combined with the known music.
In vocal music, recitatives are often a particularly difficult challenge for reconstruction: when Bach parodied his own vocal music, he reused music of arias, duets and choruses for the new work, but recitatives with different lyrics were less suitable for such transcriptions. For example, when he adapted Vereinigte Zwietracht der wechselnden Saiten, BWV 207, one of his secular cantatas, [12] into Auf, schmetternde Töne der muntern Trompeten, BWV 207a, for a different occasion, he reused the music of all movements except the music of the recitative movements 2, 4 and 6: he composed new music for the recitatives of the later work. [13] An exception appears to have been when he parodied the Michaelmas cantata BWV 248a, recitatives and all, into the sixth part of his Christmas Oratorio: how exactly he proceeded with this adaptation can however not be ascertained while the text of the BWV 248a cantata went lost. [14] Reconstruction of recitatives may depend on borrowing music of recitatives with somewhat similar lyrics (e.g. Simon Heighes 1995), [15] or re-composing recitatives in the style of Bach (e.g. Ton Koopman 2000). [16]
Reconstruction of chorale movements of lost church music is helped by the fact that hundreds of Bach's four-part chorales survive, including separate chorales such as BWV 253–438 and 1122–1126, which are most likely nearly exclusively chorale settings from otherwise lost larger vocal works. With some educated guesswork Bach scholars such as Friedrich Smend and Klaus Häfner have coupled extant chorale settings with hymn verses in librettos of otherwise lost works. [17]
Cantatas
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Bach likely composed around 300 church cantatas, of which around 200 are extant. In other words, nearly two of his five cantata cycles were lost: the larger part of what is conventionally indicated as his fourth and fifth cycles is lost. For his secular cantatas, less than half of the around 50 known works are fully extant. Several dozens of Bach cantata librettos survive without music, many of these by Picander, published in his Ernst-Schertzhaffte und Satyrische Gedichte : a few of these are at least partially reconstructible based on known works.
Examples of at least partially reconstructed Bach cantatas include:
- Steigt freudig in die Luft, BWV 36a
- Die Freude reget sich, BWV 36b
- Der Himmel dacht auf Anhalts Ruhm und Glück, BWV 66a
- Erwählte Pleißenstadt, BWV 216a
- Entfliehet, verschwindet, entweichet, ihr Sorgen, BWV 249a
- Entfernet euch, ihr heitern Sterne, BWV Anh. 9
- Böse Welt, schmäh immerhin, the cantata for Judica of Picander's 1728–29 libretto cycle, a 1983 reconstruction by Gustav Adolf Theill, based on music of the secular cantata BWV 209. [18]
Passions, oratorios, and church music in Latin
Reconstructions range from small repairs (e.g. the last measures of laudes "D" of the Magnificat in E-flat major, BWV 243a), [19] to reconstructions of entire Passions (e.g. several reconstructions of the St Mark Passion, BWV 247). [20]
