Keyboard Theory for the New Age Phreak

by autocode

Besides being a computer enthusiast, I am also a musician.

Lately, I have taken an interest in telephone frequencies.  This wasn't always the case though.

It wasn't until recently that I had the pleasure of hearing some idiot know-it-alls at a music store babbling about how you can tune your guitar to a telephone's dial tone because it's the pitch A, or gasp an E (both incorrect observations) that the relationship between music frequencies and phone frequencies began to interest me.

Thinking about the two further I thought to myself wouldn't it be cool to know what frequencies make up an 88-key piano, and then try and duplicate a phone's dial tone frequency by playing it?  My findings are as follows.

Here are all of the 88 frequencies in Hz for each piano key.  Music letter association is also provided, except for letters that require accidentals i.e., sharps (#), and flats (b).

A0 B0 C1 D1 27.500 29.135 30.868 32.703 34.648 36.708 E1 F1 G1 38.891 41.203 43.654 46.249 48.999 51.913 A1 B1 C2 D2 55.00 58.270 61.735 65.406 69.269 73.416 E2 F2 G2 777.82 82.407 87.307 92.499 97.999 103.83 A2 B2 C3 D3 110.00 116.34 123.47 130.81 138.59 146.83 E3 F3 G3 155.36 164.81 174.61 185.00 196.00 207.65 A3 B3 C4 D4 220.00 233.08 246.94 261.63 277.18 293.66 E4 F4 G4 311.13 329.63 349.23 369.99 392.00 415.30 A4 B4 C5 D5 440.00 466.16 493.88 523.25 554.37 587.331 E5 F5 G5 622.23 659.26 698.46 739.99 783.99 830.61 A5 B4 C6 D6 880.00 932.33 987.77 1046.5 1108.7 1174.7 E6 F6 G6 1244 .5 1318.5 1396.9 1480.0 1568.0 1661.2 A6 B6 C7 D7 1760.0 1864.7 1975.5 2093.0 2217.5 2349.3 E7 F7 G7 2489.0 2637.0 2793.0 2960.0 3136.0 3322.4 A7 B7 C8 3520.0 3729.3 3951.1 4186.0

A dial tone consists of two frequencies: 350 Hz (?) and 440 Hz (A4).

One idiot at the music store was partially right.  The reason why I have put a question mark next to the 350 Hz instead of the music letter equivalent is because if you look at the frequency music letter chart I created above, you will see that there is no frequency that matches 350 Hz exactly.  But there is one that is very close: 349.23 (F4).

As a matter of fact, this was something I ran into a lot while trying to match other phone frequencies.  But back to our dial tone frequency example.  Now that you know what music letters/frequencies make a dial tone, I'll explain how to find them on a piano's keyboard.

The black and white keys on a piano's keyboard are grouped in a repeating pattern.

Wherever you see two black keys grouped together, the white keys to the left of them in order are C and B.  Wherever you see three black keys grouped together, the white keys in order are F and E.  From there you can fill in the rest of the white key letters on the piano by using the musical alphabet A, B, C, D, E, F, and G that you thought was so band-geeky to learn in middle school.  Hint:  The key to the left of B is A.

Now that we know this, to find F4 (349.23 Hz), go to the extreme left of the piano's keyboard to find the lowest F (F1) and go right (up in frequency) until you find the fourth F (this includes the F you started on).

Congratulations, you've found the first tone of the two tones needed for a dial tone.

If you haven't figured out by now what the number next to the F means, you should stop reading this article now.

A4 (440 Hz) can be found by... you get the picture.

All right, let's play them together.

At first they don't sound like a dial tone, but after listening real close you can hear it!  I recommend holding down the piano's sustain pedal to have the two notes ring together constantly like you would hear on a telephone if it was off the hook.

I also recommend playing both tones on a real retro Fender Rhodes Organ.  There's something about that instrument that makes them sound really phone-like.

I hope you enjoyed my little article and that it leads to further experimentation for you.  It really just scratches the surface of what can be done with music and frequencies from various other sources, especially ones that may be controversial.