After the ceremony, the "All I Ask" singer took to Twitter to explain the sound issues -- including the apparent flatness -- that plagued the performance.
"The piano mics fell on to the piano strings, that's what the guitar sound was. It made it sound out of tune. Sh-- happens," Adele wrote.
However, Adele turned out to be a little grateful for the sound issues, since it gave her a reason to eat her feelings, animal-style.
Because of it though... I'm treating myself to an in n out. So maybe it was worth it.— Adele (@Adele) February 16, 2016
Watch Adele's full Grammys performance below.