This application produces tones of well-defined frequencies, in order to tune music instruments.
The tone range equals A0 to C8, divided by half tones, i. e. all 88 tones of a piano.
The base frequency is predefined to A4 = 440 Hz, but can be adjusted in steps of 1 Hz.
The frequency of the current generated tone is visible. It may be necessary to use an external speaker or headphone, because the speaker of the iPhone or iPod Touch may not be able to create the tone.