I was in the car letting it warm up this morning (had to go somewhere). The radio was blastin’ some sweet rock tunes, and I
pushed the gas pedal while in neutral. I don’t know why I did it, but I did. Miraculously, the motor was running right at 2200 RPM, spot on. As a strange coincidence, the song was in “A”. It made the whole car tingle with music… 5 octaves above the song. Now, whenever I want to know what key a song is in, I can just run the car through RPMs that are easily divisible by standard frequencies. I tried it on the highway. Totally identified something at roughly 2600 RPM, which I checked and is C. It works. Try it.
Jesse, again with the units! Your car was more likely playing a note closer to 3 octaves below the song. A is 440 Hz, 2200 rpm is 36.67 Hz, but since there are 4 asplosions in one revolution that’s more like 146.67 Hz is the note your car was ‘playing’.
Oh yeah. Regardless, it works.