The common instruction for tuning clean unisons is to tune the unison so that there is no beating in the higher partials.

This is not exactly true. The instruction—do not leave any partials beating—is directed at beginners whose unisons are so bad that we can actually hear the partials beating and we say, "What? Can't you hear that? Those partials are beating. The partials are not supposed to be beating!"

Telling someone that the "partials should not be beating" is meant to help beginners stop tuning horrible unisons. Tuning pure unisons is a gradual learning curve. Simply having beatless partials is not enough to achieve this, but it's a step in the right direction.

This confusion is worsened when we talk about what to listen for. In the previous lesson, we talked about how important it is to zero in on specific partials to prevent non-beating, but in this lesson, we advocate the opposite—learning to listen to the whole sound of the unison, which allows us to more easily identify out-of-tune unisons.

The first video below gives you some background on this new idea, and the 2nd gives you some examples.