Understanding Piano Inertia - Creating Your Ideal Touch

Understanding Inertia

Keys and hammers have inertia. This means that once in motion, keys and hammers resist changes in their direction of movement. They also resist changes in speed.

The inertial touch of a piano is what it feels like to force the hammers to change direction or to accelerate… for example… inertial touch is what it feels like to get a hammer moving towards the strings, after an instant before, it rebounded with significant force from the strings.

The faster a piano is played, the more pronounced the inertia of the keys and hammers is felt.

The higher the inertia of the action, the harder it is to get the parts to stop or slow down musically.

In short, inertia means the keys and hammers have a mind of their own, and it’s not a terribly musical mind.

Targeting Inertia

So the goal is to be able to target and control the amount of inertia contained in an action. Targeting the inertia will allow a pianist to comfortably control an action, rather than be controlled by the action.

Until recently, technicians did not have the intellectual tools necessary to target inertial touch accurately. We could measure and carefully balance the keys to the hammers while the action was at rest, but we could only guess what the action might actually feel like in play.

It was a high stakes guessing game, based on lots of experience and inevitable mistakes… sometimes it worked, and sometimes it didn’t.

Creating Your Ideal Touch

Computer aided design tools have thankfully changed this. The design tools, combined with appropriate skills and experience, allow a designer to accurately aim at and hit inertial targets. The designer can now achieve predictable, repeatable and customized inertial touch targets.

So, after defining ideal touch, these tools allow me to target and create that touch.

I target inertial forces based on John Rhodes’ and Darryl Fandrich’s fine analysis of inertial action forces. I design my key and action leverages using a geometrical optimization protocol taught to me by Bruce Clark.

With the analytic tools, I can accurately determine what an existing action’s inertial touch is, and then reproduce that touch precisely in a new or rebuilt action. I can also tweak the inertial touch of an existing action.

My fee for a 3-1/2 hr Inertial Touch Consultation is $350. It is an on-site consultation, where I analyze and quantify the inertia of you piano action, and help you to begin defining your ideal touch.