PianoMeter is a piano tuning app that will transform your Android device into a professional quality electronic tuning aid.

NOTE
The "free" version of this app is primarily for evaluation, and it only allows you to tune notes on the piano between C3 and C5. To tune the entire piano you will need to buy an upgrade through an in-app purchase.

What makes PianoMeter unique
Unlike regular chromatic tuning apps that simply tune to a pre-calculated equal temperament, this app actively measures the tonal characteristics of each note and automatically calculates the ideal “stretch” or offset from equal temperament. In other words, it creates a custom tuning for your piano with the best compromise between intervals like fifths, fourths, octaves, and twelfths, the way aural piano tuners do when fine-tuning.

Functionality and pricing
There are three levels of functionality: a free (evaluation) version, a paid "plus" version with basic tuning functionality, and a "professional" version with features geared towards professional piano tuners. The extra functionality is unlocked through one-time in-app purchases.

The Free version includes the following functionality:
• Tuning functionality for the mid-range of the piano only
• Automatic note detection
• Ability to measure each note on the piano to see how its current tuning compares to the ideal tuning curve (see if a piano is roughly in tune)
• Swipe in the graphing area to show a live frequency spectrum or the inharmonicity of measured notes.

Upgrading to "Plus" adds the following functionality:
• Tuning functionality for the entire piano
• Tune to frequency standards other than A=440
• Tune to historical or custom temperaments
• Calibrate device to an external frequency source

Upgrading to Professional unlocks all features of the "Plus" version, plus the following:
• Save and load tuning files, so a piano doesn't need to be re-measured each time it is tuned
• Pitch raise mode that calculates overpull for an initial first pass "rough" tuning (for pianos that are extremely flat)
• Custom tuning styles: create a custom tuning curve by adjusting interval weighting and stretch
• Access to all future features and enhancements

Upgrade costs:
Free to Plus (approximately US$25)
Free to Pro (approximately US$300)
Plus to Pro (approximately US$275)

Note about permissions
This app requires permission to access the microphone on your device and permission to read and write files.