Keyboard specs, and which ones matter

Keyboard marketing is unusual in how completely it inverts the priority order. The headline is nearly always the voice count, which is close to meaningless, while the specification that decides whether the instrument is usable gets a line in a table.

This page reorders the sheet.

The four that matter

1. Full-size keys. The standard width every piano in the world uses. Narrower keys teach a hand span that is wrong on every other instrument the player will ever touch, and physical habits are far harder to unlearn than to learn. This is the one specification we treat as non-negotiable, which is why the Casio Casiotone CT-S200#ad is in our picks despite being an inexpensive board — it does not compromise here.

2. Touch response. Also called touch sensitivity or velocity sensitivity. The keyboard measures how fast the key goes down and plays proportionally louder. Without it, every note is the same volume regardless of how you play, which makes dynamics impossible and makes practice actively misleading.

3. Key action. What the key feels like. Synth action is light and springy; semi-weighted adds resistance; a graded hammer action puts a real weighted lever under each key and makes the low notes heavier than the high ones, like an acoustic piano. The Yamaha P-145#ad uses a graded hammer action and that is most of what its price buys. The full argument is in weighted versus unweighted keys.

4. Key count. 61 covers essentially all beginner material; 88 covers everything written for piano. It is a real ceiling rather than a preference, and where it bites is set out in 61 versus 88 keys.

Polyphony, properly explained

Polyphony is the number of notes the sound engine can produce simultaneously, and it is the one spec-sheet number that is genuinely worth reading.

The confusion is that it does not mean fingers. Several things consume the pool at once:

Sustained notes still count. Hold the sustain pedal and play a passage, and every note that is still ringing is still using a voice. This is the situation that exhausts low polyphony first.

Layered sounds double it. Playing piano and strings together means each key consumes two.

Accompaniment uses it. Auto-rhythm and backing styles are notes too.

When the limit is reached, the board silently drops the oldest notes. You do not get an error; you get a chord that quietly loses its bass while you are holding the pedal, which sounds like the instrument failing at random.

Practically: below 32 is a real problem, 48 is fine for a beginner, and 64 or more is more than enough. Above that the number stops meaning anything to a learner.

The specs that do not matter

Voice count. The big number on the box. A board advertising several hundred sounds has a good piano, a decent electric piano, a usable organ, some strings, and several hundred variations nobody plays twice. Judge a board by whether its piano sound is good, because that is the one you will use.

The Casio Casiotone CT-S1#ad makes this argument explicitly: it carries a deliberately short voice list and spends the engineering on the piano sound and the speakers. For a player learning piano, that is the right trade and it is the opposite of what the market rewards.

Rhythm and accompaniment styles. Fun for a week. Some players genuinely use them and most switch them on twice. The Yamaha PSR-E383#ad has a substantial set and a lesson system, and it is a legitimate reason to buy it — if you know you are the sort of person who will use them.

Built-in song libraries. Useful for the lesson features that reference them, otherwise decoration.

Speaker wattage. Small numbers on small cabinets. Every board in this class sounds better through headphones, and comparing wattage figures between manufacturers tells you very little.

Two specs that are quietly useful

A proper sustain pedal socket. Written piano music assumes a sustain pedal within months. A board with no socket, or one that only accepts a sliding plastic footswitch, has a real limitation. Details in keyboard accessories you actually need.

A headphone output. Present on essentially everything, and worth confirming. It is the feature that decides whether practice can happen in the evening, and it is the only reason a keyboard can be silent in a shared house.

Reading a spec sheet in ninety seconds

Find the key width. If it does not say full-size, stop.

Find touch response. If it is absent, stop — that is a below-the-floor instrument regardless of anything else on the sheet.

Find the action type, and decide whether you need weighted keys based on what you intend to play rather than on aspiration.

Find polyphony. Anything 48 or above is fine.

Then ignore the rest of the page. The remaining specs are how manufacturers differentiate products that are, in the ways that matter to a learner, the same. Where the line between acceptable and not sits is in are cheap keyboards worth it.