He had been scheduled to return to Carnegie the following March for another of the solo recitals that have done the most to create his legend — like the one captured on the recording “Budapest Concert,” to be released on Oct. 30. But that Carnegie performance was abruptly canceled, along with the rest of his concert calendar. At the time, Mr. Jarrett’s longtime record label, ECM, cited unspecified health issues. There has been no official update in the two years since. But this month Mr. Jarrett, 75, broke the silence, plainly stating what happened to him: a stroke in late February 2018, followed by another one that May. It is unlikely he will ever perform in public again.