Following Nikolaus Harnoncourt’s death earlier this year, only months after announcing his retirement, it seemed that the two Beethoven Symphonies recently released on Sony would be his final word on disc. But apparently it was his wish that this Missa Solemnis, taped during concerts and rehearsals in Graz last summer, should be his final recording. It’s no grand last testament, though: unsurprisingly for Harnoncourt, there is a sense of searching throughout the performance, perhaps partly because he had never before recorded the work with his own Concentus Musicus Wien, and their period instruments, gut strings and lower pitch threw up new sonorities and new puzzles for his questing brain to solve. The solo quartet, led by the poised soprano Laura Aikin, is light-voiced, and with supple singing from the Arnold Schoenberg Chor, it’s a gentle performance overall. But Harnoncourt’s masterly control of the larger structure means that within those parameters, the moments of jubilation make all their impact.