Phone Numbers as Melodies

Because nature is full of harmonic sounds (sounds which contain frequencies that are multiples of each other or that are both multiples of the same base frequency), the frequencies making up DTMF tones were chosen to be not harmonic at all.

They are not even related to each other in the same way today's musical tones are. You can make one or two of the DTMF frequencies line up with musical notes (different pairs depending on how you tune your instruments), but that's about it.

DTMF frequencies (left) vs Musical Scales (right)

While this makes the phone electronics cheaper to build and more reliable, it makes playing musical tones with your phone keypad somewhat difficult: phone keypads make really bad instruments -- they are like a piano with 12 keys none of which sound right by themselves, let alone played together.

Having said all this, many melodies can be played and are somewhat recognizable. You should try it yourself next time you call a friend.

WARNING: If you pick up your phone and start punching numbers, you will probably get connected to somewhere and you will pay for the call.