Note: PitchCalc is no longer available on the Apple Store, as I have become an Apple employee since it was published.

I’ve submitted my first application to the Apple iPhone/iPod Touch App Store, called PitchCalc. It calculates the frequencies of various equal-tempered pitches with tuning offsets and displays the frequency ratios between them.

PitchCalc Icon

When you launch it, it presents you with the following screen:

PitchCalc Main Screen

The main interface is the two sliders you see, which allow you to adjust the pitch in coarse and fine increments. The top slider selects a pitch (initially A0; i.e., the pitch class A in the “0” octave), and the bottom slider lets you tune that pitch sharp or flat in increments of a cent (1/100 of a semitone), up to a full semitone (100 cents) sharp or flat. You may move the sliders by sliding their control pads or by tapping the treble/bass or sharp/flat buttons to move them by a single unit.

Under the sliders in large type, you see the frequency of the selected note. The initial reference note (A0 +0 cents) is 440.0000 Hertz (abbreviated Hz).

Beneath the frequency readout you see the ratio of the selected note’s frequency as compared to a reference frequency. Initially the reference frequency is set to 440.0000 Hz, so the ratio starts at 1.000000.

Here we see that the pitch E1 +2 cents represents 660.0172 Hz, which is a ratio of 1.500039 compared to the reference A440.

PitchCalc Comparison

(This means that if you play an E1 against an A0, playing it in a “true” equal-tempered tuning will beat slightly, but playing it 2 cents sharper at 660.0172 will result in a purer tone.)

After you’ve moved the sliders around and selected a new note, you can set the new note to be the reference frequency by tapping the button labeled SetRef which saves the current note as the reference frequency (and note that the ratio readout changes back to 1.000000).

Obviously this is useful when you are playing in a key other than A:

PitchCalc E0 vs. C0

When you’re finished and want to reset your pitch, you can push the Reset button to reset the sliders back to A0. If your reference is set to something other than A440, a second push will set it back to A440 (and disable the button until you move the sliders again).

PitchCalc is priced at $0.99. Updates will be free and will enable more functionality, such as specifying a target frequency and finding the note and tuning offset that it represents, and specifying a base note and target ratio and finding the frequency and note and tuning offset that gives that ratio.

Note: PitchCalc is no longer available on the Apple Store, as I have become an Apple employee since it was published.