This is Celebrate Bach Day on Google. Bach's final composition was missing its 'final' page. Did it go missing? Did he compose it it but had not written it down? Did he deliberately leave it incomplete, by that meaning, is that what he intended?
So are there 47 bars missing? How do we know this? This number is the result of much analysis and thinking. What is known is that in these bars, Bach would have combined the main theme of the entire work with the other three themes of his final fugue.
There have been many written completions by others. How many? I haven't found that answer. But there's a lot of time between 1750 when Bach died and the 19th century when the Bach Revival occurred. And even more time to our 21st century. All the great composers have referenced Bach, so this unfinished fugue has received much attention.
There was a period of decline in his popularity after his death in 1750. The decline is easy to explain. His work was so complex that few could perform it. He did not pursue publication of the majority of his work - only the final compositions. Most of his work was created for teaching. And the musical trend after him was towards simple, more homophonic sounds. His music manuscripts were dispersed to students and inheritors, who did not actively preserve it. What did persevere was the use of his music for teaching keyboarding and counterpoint. So a gap occurred between his death and 1781.
The Revival was supposedly sparked by Felix Mendelssohn's performance of the St. Matthew Passion in 1829. Current thinking is that this performance was a major milestone along the way, rather than the beginning. His son, Carl Philipp Emanuel Bach left a large collection of his father's manuscripts to the German state library after his death in 1788. There they were made publicly available. His biography was published in 1802 and it is considered key to the Bach Revival.
Most mysterious at the last notes in the fugue is a note in the handwriting of Carl Philipp Emanuel Bach, stating: "At the point where the composer introduces the name BACH [for which the English notation would be B♭–A–C–B♮] in the countersubject to this fugue, the composer died." How wonderfully dramatic, but it has been successfully questioned and disputed based on Bach's declining abilities before he died.
That question of "How many completions are there of the Unfinished Fugue?" still intrigues me. But I found this in theepochtimes.com article. And it seems so satisfying as the conclusive completion.
"Fretwork musicians perform their own completion. There are many completions of Bach’s 15th counterpoint in “The Art of Fugue,” but Boothby’s is unique: “The parts of the fugue are proportionate to each other. The first section is 1.4 times the size of the second, and the second is 1.4 times the third, and so forth,” Boothby said. Taking that relationship to its logical conclusion, the fugue would have to be 47 bars, he explained. "