The two most common methods of tuner visualization are a needle or a scrolling line, both of which represent the distance in cents between the note being played and your target note.
Instruments create frequencies with a bit of variability. In order for needle/line-based visualizations to not jump around too much, the activity of the needle/line is “smoothed” to make it easier to read. This has the side effect of hiding the distribution of frequencies that occur you when you play a single note on your instrument. The visualization in One Click Tuner fixes this by showing the distribution of frequencies around the target.
Just about any musical instrument can be tuned with One Click Tuner. The exceptions are instruments with low ranges like double bass (iPhone microphones poorly track low frequences) and piano (see Railsback curve). One Click Tuner is perfect for: