Choosing a digital piano: weighted keys, 88 keys, polyphony and sound

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A digital piano is how many people start, especially in a flat where an acoustic piano would be too loud, too big or too hard to keep in tune. The range of instruments is wide, and the specifications can be confusing. This guide explains what the terms mean and which ones matter most for a learner. It deliberately names no brands: try instruments in person where you can and decide by touch and sound.

Digital piano or keyboard?

The words are used loosely, but broadly:

A digital piano aims to imitate an acoustic piano: full-size weighted keys, usually 88 of them, and a focus on piano sound.
A keyboard is often lighter and cheaper, with unweighted keys, fewer keys and many built-in sounds and rhythms.

A keyboard can be a fine way to try music for fun, but if your goal is to learn piano, look for the features below.

Weighted and hammer action

On an acoustic piano, each key moves a hammer that strikes a string, which gives the keys weight and resistance. Digital pianos imitate this in different ways:

Unweighted or synth-action keys are light and springy. Easy to press, but they do not build the finger control you need for an acoustic piano.
Semi-weighted keys add some resistance.
Weighted or hammer action keys use a mechanism to imitate the feel of an acoustic piano. Many also use graded weighting, where lower keys feel heavier than higher ones, as on an acoustic piano.

For learning piano, weighted hammer action is the feature that matters most. Players who learn on light keys often find an acoustic piano tiring and hard to control.

88 keys

A standard piano has 88 keys. Many beginner pieces use only the middle of the keyboard, so fewer keys can work at first, but you will run out of room as you progress, and much of the repertoire uses the full range. If you can, choose 88.

Touch sensitivity

Touch sensitivity (sometimes called velocity sensitivity) means the instrument plays louder when you strike a key harder and softer when you press gently. Without it, you cannot practise dynamics, which are a basic part of playing expressively. Treat this as essential. Some instruments also let you adjust the sensitivity to suit your touch.

Polyphony

Polyphony is the maximum number of notes the instrument can sound at once. This matters more than it seems: when you hold the sustain pedal, every note you play keeps sounding, and some sounds use more than one voice per note. If the polyphony runs out, earlier notes cut off abruptly. Higher polyphony is better, and very low figures are worth avoiding for piano playing. Check the specification sheet.

The sustain pedal

Many instruments come with a small square footswitch. A proper piano-style pedal is more comfortable and closer to the real thing, and some support half-pedalling. A pedal is inexpensive to upgrade later if needed, but make sure the instrument has a socket for one.

Speakers and headphones

Built-in speakers vary widely. Listen in person if you can, at both low and high volume, and play low notes to hear whether they sound full or thin.
Headphones are one of the biggest practical advantages of a digital piano: you can practise late at night without disturbing anyone. Check what kind of headphone socket it has, and whether it has two if you plan to have lessons alongside a teacher.

Wear comfortable, closed headphones for long sessions, and keep the volume moderate.

Other things to check

Stand and bench: a stable stand that does not wobble, and a bench at the right height. Some instruments come as a cabinet with a built-in stand; others need a separate stand.
Portability: a slab-style instrument can be moved, but weighted ones are still heavy.
Connections: a USB or MIDI connection lets you use learning apps or recording software on a computer or tablet.
Built-in metronome: handy, though a phone app works just as well.
Space: measure the spot where it will live.

Buying second-hand

Digital pianos are often sold second-hand when people give up. Test every key for even response, check the pedal, listen for buzzing from the speakers, and make sure the power supply is included.

Try before you decide

Specifications only go so far. Two instruments with similar specs can feel quite different under the fingers. If you can, play several in a shop, ideally including an acoustic piano for comparison, and pick the one whose touch you like. What are you choosing between, or what did you wish you had known before buying? Share it in the comments.