String Tuner

Google Play App page on Google Play

Lower Higher
This tune is flat.
The string needs to be tightened.
This tune is sharp.
The string needs to be loosened.

The string theory

The sound of a vibrating string can be approximated by a harmonic series, a sequence of simple tones (sine waves) with frequencies that are integer multiples of the fundamental. In a chord, some of these harmonics play more important role than the fundamental because they match the harmonics of the other strings. The following picture shows spectrum of 2 notes that make a perfect fifth (7 semitones apart), G3 and D4.


Notice that third harmonic of one string matches second harmonic of the other. They are close enough to be perceived as one tone, but the difference in frequency can produce beats or roughness, making the chord sound dissonant [1].

Many electronic tuners only indicate the fundamental frequency, although the other harmonics may be more important. And we cannot assume they are exact multiples of the fundamental because real strings have some inharmonicity [2].

This application uses independent phase-locked loops (PLL) to track 6 harmonics of the string.

Remember that you should always end with tightening the string rather than loosening it. [3]


1. Roederer, J.G. The Physics and Psychophysics of Music - An Introduction
Springer, 2009

2. Joe Wolfe, UNSW. How harmonic are harmonics?

3. When tuning a guitar... - StackExchange Music.

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