All Beethoven scholars have reason to be grateful to Schindler - and angry with him - in equal measure.
Schindler was a violinist who introduced himself into Beethoven's circle in about 1822. He made himself indispensable to Beethoven, who was by now totally deaf.
He helped him in his dealings with his friends as well as publishers, offering advice and taking administrative chores off Beethoven's shoulders.
But he was over-protective of Beethoven, keeping his friends away and erecting a metaphorical wall around him.
At first Beethoven was grateful but became tired of his obsequiousness.
He dismissed Schindler after the concert which premiered the Ninth Symphony in May 1824, accusing him of withholding receipts from him. But Schindler was back in favour two years later and remained with Beethoven until his death.
Schindler was determined to secure Beethoven's reputation for future generations as a God-like figure. He examined all Beethoven's Conversation Books in minute detail, destroying any that cast Beethoven in any adverse light. Into others he inserted spurious details which, among other things, cast himself in a favourable light and exaggerated his influence with Beethoven.
He also wrote the first major biography of Beethoven, but that too contains many inaccuracies.
It was not until the 20th century that scholars were able to unravel the truth from the fiction in the material Schindler left. Today his insights are valuable, but only when studied alongside modern scholarship's corrections.