Weighted, hammer action or semi-weighted keyboard — what's the difference?

The most important specification of a digital piano explained without jargon. How touch-sensitive, semi-weighted and weighted hammer-action keyboards differ, and what that means for learning.

If you were to pay attention to a single specification of a digital piano, it should be the way the keyboard works. It decides how the instrument responds to your fingers, what habits it builds and whether the move to an acoustic piano will be smooth.

The trouble is that the naming can mislead. "Touch-sensitive", "semi-weighted", "weighted", "hammer action" — these terms describe different things and sometimes get mixed up. Let's sort them out.

Touch-sensitive is not the same as weighted

That is the commonest misunderstanding. Touch-sensitive means the instrument responds to the force of the stroke: strike harder and it sounds louder. That is a property of the electronics, not of the mechanics.

Weighted speaks of something else — of the resistancethe key offers the finger. That is a physical property of the construction.

So you can have a touch-sensitive keyboard that is nonetheless light: it responds to force, but the keys are sprung. A good digital piano combines the two.

Three levels of action

Touch-sensitive (light) keyboard

The key returns thanks to a spring. The finger's work resembles pressing a computer keyboard. You'll meet it in arranger keyboards and in the cheapest instruments.

Advantage: lightness, low price, low weight of the instrument.
Disadvantage: it doesn't teach control, because there is nothing to control. The fingers build no strength.

Semi-weighted keyboard

A weight is added to the key, increasing the resistance. There is no full hammer action, but the difference from a light keyboard is clearly felt.

Advantage: it teaches you to differentiate volume while remaining pleasant for a beginner who has no finger strength yet.
Disadvantage: it doesn't fully reproduce the behaviour of an acoustic.

This keyboard — 88 touch-sensitive, semi-weighted keys — is fitted to the V5N model and its colour variants V5WN and V5NB.

Weighted keyboard with hammer action

Here a real hammer works beneath the key — a lever with a weight, reproducing the mechanics of an acoustic piano. Pressing the key, you set a mass in motion rather than compressing a spring.

The effect is twofold. First, the resistance is natural and "inertial" — the key responds to the manner of the stroke, not only to its force. Second, in good constructions the resistance varies along the keyboard: the lower notes are heavier, the upper ones lighter, just as on an acoustic, where the bass hammers are bigger.

Advantage: it builds technique that transfers to an acoustic piano.
Disadvantage: a higher price and a greater weight of the instrument.

Hammer action is fitted to these models: V9N, V9NB, V9WN, V10NB and V11B.

What that means in practice when learning

Imagine a pupil who practises for a year on a light keyboard and then sits down at a piano in music school. Their fingers have learned to strike shallowly, because there was no need to go deeper. On an acoustic the same movements produce a quiet and uneven sound.

The reverse situation is far easier. Anyone who has practised on hammer action will manage on a lighter keyboard straight away.

Hence the simple rule: the more serious the plans, the heavier the keyboard.

Which to choose — specific situations

• A child beginning to learn, with no certainty yet about commitment — semi-weighted is a sensible compromise. It gives control over dynamics without tiring weak fingers.
• Lessons with a teacher, music school, exams — hammer action, without hesitation.
• An adult returning to playing after years — hammer action, because motor memory from an acoustic will pick up the difference at once.
• Light-music playing, accompaniment, arranging — semi-weighted will do perfectly well.

What the name alone doesn't tell you

It is worth remembering that marketing terms can be elastic. Instead of relying on a slogan from a leaflet, check in the specification whether the manufacturer explicitly writes about hammer action, and if you have the chance — play it. A few minutes at the instrument says more than a page of description.

A good test is to play the same note as quietly and as loudly as you can. On a good keyboard the difference is smooth and predictable rather than abrupt.

Summary

A touch-sensitive keyboard responds to force. A weighted one offers resistance. Hammer action reproduces the workings of an acoustic piano. These are three different things, and only their combination gives an instrument on which technique develops without later corrections.

You'll find the keyboard specification of every model among the specifications in the digital pianos.