I liked what Anthony Payne did with the sketches of Elgar's Third Symphony. I have three or four different versions on CD and play them often. It's true that Elgar on his deathbed forbade anyone trying to complete the sketches, but then why didn't he have them destroyed?

 

I have mixed feelings on this topic. I'm glad to have a completed version (or two) of Mahler's 10th symphony. He himself felt he had completed it "in the sketch". Of course, much of it lacks his superb orchestration, which would be hard enough to approximate successfully, never mind the chorus of angry criticisms any such attempt would doubtless provoke. (Putting in so many notes not composed by Mahler, etc.)
Mozart certainly wanted his Requiem completed even when he was to too ill to do it himself, as he very much needed the substantial fee his widow ultimately was able to collect, iirc, thanks to the completion by his student and secretary Sussmayr. But there I'm not entirely happy with the result.
A famous similar example in literature: Marcel Proust worked desperately hard to complete his massive, complex masterpiece Remembrance of Things Past before he died. Fortunately for him, he was wealthy and could afford a full time secretary to assist him. He didn't quite succeed, though, and some rough spots remained at his death. But he was wise enough to fully complete his ending and everything else that was truly central. The few rough edges and undeveloped ideas that remain don't detract significantly from the result.
Puccini couldn't bring himself to finish Turandot, so I suppose someone else had to do it, even if the result was competent but unremarkable.
But if a composer voluntarily chooses to abandon a work, I agree that choice should generally be respected.

 

I agree that the composer's wishes should be respected. As in other arts, for example: Fred Astaire had a fascinating life and I, for one, would enjoy a well-done "biopic" film. But Fred stipulated that no one should ever portray him. And so far that wish has been respected (as far as I know.) I think a great artist, who gives pleasure to so many, is entitled to that.

 

It's fascinating to compare the 'original ' version of Vaughn Williams London Symphony, which he had performed publicly, with the official final version, and ditto for the two versions of Sibelius 5. In both cases the Composers had second thoughts after hearing their works in Concert. Rachmaninov also did similar things.
I wonder, if Mahler had been granted another decade of Composing, and had a chance to not only complete the 10th, but to hear the 9th and Das Lied performed, what changes he would have made to those scores. He made the right call in dropping 'Blumine' from the First, lovely though that piece is

 

I don't see why a composer would even care whether we try to complete a work after his death, so long as we don't try to pass off our part of the work as authentic. We know very well that the final scene of Turandot isn't Puccini's, so even if we don't think it's up to his standard it's no blot on his reputation. If we want to stop the performance with Liu's suicide we can do that, as Toscanini did at the first performance, out of "respect," but what sense does that make for anyone wanting to see an opera? In most cases it's only composers' last works that lie unfinished, so it isn't as if we're screwing around with the body of their achievement. Personally, I don't need to hear a fourth movement for Bruckner's 9th, or any additions to Schubert's 8th, but if you do, well, have at it. Like many others, I enjoy the Symphony #3 by Elgar/Payne, and that's how the work is quite properly identified.

Completions, properly identified, seem to me no more intrinsically offensive or improper than transcriptions or orchestrations by people other than the composer. The works continue to exist in their original form.

 

I don't see why a composer would even care whether we try to complete a work after his death...

I think it's safe to say that the composer won't care even one tiny bit.

 

As to Mahler's Tenth, I'm wondering if his dictum to Klemperer might apply: "If, after my death, something doesn't sound right, then change it. You have not only the right but the duty to do so." Is it absolutely necessary for an admitted completion of the Tenth to sound exactly like Mahler, or is it appropriate if it simply sounds "right?"

 

Doubtless some completions are done as a tribute or upon the composer's wishes from detailed sketches. Some, however, are a product of just wanting more or - even worse - of having a piece of news to broadcast to the world, like whenever some little scrap of Mozart's is discovered and 'premièred'. No-one really cares whether or not it's authentic. As if adding this would somehow have an effect above the body of work already left behind. I'm generally happy to have the work a composer left as his/her legacy.

I can't imagine this being tolerated quite as much in many other artistic areas. Would a Leonardo canvas sketch turned into a finished painting be as warmly welcomed? Or fragments of a lost Hitchcock film with invented dialogue and re-shot scenes? I realise these are not pure analogues, but are you really getting the work of the artist in all these cases?