[Somehow the sequence of text in this entry became garbled; I've reposted it with the text in the correct order. Apologies to my legions of loyal readers. You are legion, aren't you?]
Try entering this exact search string, with the asterisks and the quotation marks, into Google and see what you get:
“Composed * before * death” “program notes”
Here’s a sampling:
Mozart's Clarinet Concerto was composed in 1791, shortly before Mozart's death…
Schubert's epic late Cello Quintet, D. 956, a piece composed two months before the composer's death…As a program annotator, I regret that so many music writers fall prey to a retrospectively tragic assessment of a composer’s final works, imbuing them with some special quality simply because the composer happened to die soon after their completion. The snippets cited above give only an inkling of this sort of writing, but we’ve all seen plenty of extended examples in program notes, reviews, and liner notes, where a writer gives in to the sentimental urge to look for poignant, elegiac, or tragic qualities in music created shortly before a composer died.
The Four Last Songs, composed shortly before Strauss's death…
[Mozart’s] great clarinet concerto, composed only weeks before his death...
…the last [piano concerto Mozart] composed, less than year before his too-early death at the age of not-quite 36…
Ave Verum Corpus ... was composed six months before [Mozart’s] death, at age 35
Yes, in one or two cases, an elderly or ill composer might have known that he was at the end of his creative trajectory, and therefore took special care with works that might end up being his last. This was certainly true for J.S. Bach and his Mass in B Minor, and with Ralph Vaughan Williams’ Hodie, and perhaps even for Mozart’s unfinished Requiem.
But most composers, especially those who died young ― Mozart, Schubert, and Mendelssohn immediately come to mind ― did not expect to die when they did, and it is extremely unlikely that they regarded the music that we speak of as their “last works” as anything but “current works,” especially for composers like Mozart and Mendelssohn, who were at the height of their powers.
That those works which composers wrote shortly before their deaths ended up being their “final works” can only be known in retrospect, and were surely never perceived as “final works” by the composers themselves.
Music writers must always be able to assess a composer’s works within the context of the composer’s own lifetime, without bringing too much of our contemporary understandings into the picture. That is, when we write about, say, Mozart’s Clarinet Concerto, we must assess it on its own merits as the work of a young but mature composer, not as a “last work” written months before he died.
Unless they are hugely narcissistic, people just don’t live their lives as if everything they do is their “final work,” whether they are composers or plumbers or writers or biologists. Unless we die at an advanced age or after an extended illness, we are apt to die in the middle of it all. Like Mozart, like Mendelssohn.