Touch sensitivity and weighted keys are different concepts
A keyboard can be touch-sensitive even if the keys feel light. Weighted or hammer action describes the physical playing resistance. Many digital pianos combine both features, but the terms are not interchangeable.
What the instrument measures from the attack
Digital keyboards derive an attack value from key movement. In MIDI contexts, this is commonly called velocity. A sound engine can use that value to make a note softer or louder, or to change its timbre. The amount of change depends on the instrument and the selected sound.
What a touch curve changes
Many instruments offer settings such as Soft, Medium, or Hard. These change how your playing is mapped to volume or velocity. They do not make the key physically heavier or lighter. Yamaha documentation explicitly notes that changing touch sensitivity does not change the actual weight of the keys.
How to test touch sensitivity
- Play the same note several times, deliberately very softly and very strongly.
- Check whether you can control several useful levels in between.
- Repeat the test with a chord and with a musical phrase.
- If available, change the touch curve and see whether the response fits your playing style better.
Common misunderstandings
- “Touch-sensitive” does not automatically mean “hammer action.”
- A “Hard” touch curve does not mechanically make the keys heavier.
- Volume is not the only possible response; some sounds also change tone color.
- A fixed-velocity mode may intentionally reduce or remove dynamic response; that is a setting, not necessarily a fault.