Of course, nothing is ever as simple as it seems. Brown decided to use the Fourier calculation to decompose the song into its original frequencies and figure out the notes from there. It almost worked, save for one not- so- minor detail; the instruments didn't match up. Oh, George was definitely playing his 12 string Rickenbacker, Lennon was was playing his six string, and Paul (oh Paul) was there on bass, but there was also an unaccounted-for F note that was impossible to play with just the instruments there. "Then the solution hit me: it wasn't just those instruments. There was a piano in there as well, and that accounted for the problematic frequencies."