How to Choose a Digital Piano: Keys, Weighted Action, and Polyphony Explained

Digital piano specifications are full of terms that sound important but can be difficult to evaluate without prior experience: "graded weighted action," "triple sensor key detection," "stereo sampling" and dozens of others. Some of these matter; some are marketing language for features that won't affect your playing experience. This guide cuts through the terminology and focuses on what actually makes a meaningful difference.

The keyboard action: the most important spec

The keyboard action - how the keys feel when you press them - is the single most important specification in a digital piano. It determines how accurately the instrument replicates the physical experience of playing an acoustic piano, which directly affects your ability to develop proper piano technique.

Key action terminology explained:

Unweighted/synth-action - Light, uniform keys with spring resistance. Used in synthesisers and arranger keyboards. Not suitable for learning piano technique; the muscle memory doesn't transfer to acoustic or weighted digital pianos.

Semi-weighted - Heavier than synth-action but lighter and simpler than a full hammer action. A compromise that's not ideal for either piano technique or synthesiser use.

Weighted/hammer action - Simulates the mechanical hammer action of an acoustic piano. Keys are weighted with an internal mechanism, typically with graded weighting (heavier in the bass, lighter in the treble, mirroring acoustic piano keys). The standard for serious digital pianos.

Escapement - In an acoustic piano, the hammer mechanism has a point of slight give just before the key fully bottoms out. This allows repetition (fast note repetition) and provides a particular tactile feedback. Premium digital piano key actions include escapement simulation; budget ones don't.

Casio CDP-S110 vs PX-S1100: the action difference

The Casio CDP-S110 uses a standard hammer action without escapement. It's weighted and graded, which means you can develop basic piano technique on it. The Casio PX-S1100 uses Casio's Smart Scaled Hammer Action Keyboard, which includes escapement simulation - a more expensive mechanism that provides a more nuanced, realistic feel.

Polyphony: how much do you actually need?

Polyphony is the number of notes a digital piano can sound simultaneously. A higher polyphony number means more simultaneous notes without any being cut off.

In practice:

• Playing a simple melody with one hand uses 1-4 notes simultaneously
• Playing chords in both hands uses 6-10 simultaneously
• Playing with the sustain pedal down (which holds all notes until they decay) significantly multiplies the notes active at any time
• Layered sounds (two sounds playing simultaneously on one key) double the polyphony requirement

Minimum recommendations:

• 48-note polyphony - adequate for most beginners and intermediate learners
• 64-note polyphony - recommended for anyone using sustain pedal regularly or layering sounds
• 128-note or more - for advanced players performing complex repertoire with sustained pedal work

The Casio CDP-S110 has 48-note polyphony; the PX-S1100 has 64-note. In practice, you'll rarely hear the difference unless you're playing advanced classical repertoire with heavy sustain pedal use.

Sound quality: what "stereo sampling" actually means

Digital piano sounds are recordings (samples) of real acoustic piano notes at different pitches and dynamics. "Stereo sampling" means each note was recorded with two microphones, capturing the spatial character of the acoustic piano rather than just the pure tone. The result is a more realistic sense of the instrument occupying physical space.

More expensive digital pianos use more samples (more dynamic layers - the number of velocity levels at which the note was sampled), larger sample data, and more sophisticated interpolation between samples. This gives more nuanced, realistic tone but requires more processing power and storage.

For beginners, the sound quality difference between a £255 digital piano and a £700 one is real but not decisive. Focus on action quality and reliability first; sound quality is important but secondary.

Number of sounds

Budget digital pianos often tout a large number of built-in sounds (100+ voices are common). For piano learning, you need exactly one sound: a convincing acoustic piano. The other 99 sounds are largely irrelevant for practice purposes. Don't be distracted by voice count - a digital piano with 10 excellent sounds is more useful than one with 100 mediocre ones.

Built-in speakers

Built-in speaker quality varies significantly. Budget digital pianos have small speakers that produce adequate volume for private practice but lack the low-frequency reproduction to sound convincing at room-filling levels. If you want to hear your piano sounding full and rich, plan to either connect to external speakers or use headphones.

For practice purposes, the built-in speakers on any digital piano in the £200-500 range are perfectly functional. For performance or demonstration, you'll want external amplification.