For anyone confused by this cartoon and who enjoys long explanations:
If a keyboard instrument (harpsichord, clavichord, piano, etc.) is tuned to preserve all the precise mathematical frequency relationships for playing in one key (say, the key of C), there will be other keys that sound awful (like maybe F). So by the time of Johann Sebastian Bach they had worked out a method of piano-tuning called “tempering” in which the individual notes of the keyboard would be tuned a tiny bit off for any one key so the instrument would sound acceptable in all keys.
To demonstrate this new technology, Bach wrote a series of 24 short works in each possible key used in Western music. (Why 24? That’s the 12 notes of the octave (white and black piano keys) times two for major and minor scales.) Those works, published together, are the famous “Well-Tempered Clavier”. And if the opposite of “well-tempered” is “bad-tempered”, then, well, there you have it.
