In this test, the coincidental partials are filtered,
so they are easy to hear.

You will also see a graphical representation of where the A3C#4 is relative to F3A3 and C#4F4

The beating occurs two octaves above the top note of a M3.

Use the Filtered and Unfiltered buttons to train your ear
so that you can easily hear the beating partial within the unfiltered interval.

Each time C#4 is changed, A3C#4 will play at the new speed.

Because of the way F3 was set in this test, each M3 must increase in speed.

In a real tuning, you might end up with FAST-MEDIUM-SLOW,
but if they change speed each pair by the same degree, or ratio,
then C#4 will be accurate.