How piano hammers produce tone, what voicing means, and when Singapore's climate demands hammer replacement
Piano tone is almost entirely a function of hammer felt quality and condition. A piano can be perfectly tuned, regulated, and in excellent structural condition — and yet sound harsh, brittle, or muffled because the hammer felt is worn. Voicing (adjusting hammer felt density) costs S$120–S$350 for a full set. When voicing can no longer restore tone, full hammer replacement costs S$600–S$1,200. In Singapore's humidity, both processes need attention more frequently than in temperate climates.
A piano hammer consists of two components: a wooden moulded core (the hammer moulding or butt) and multiple layers of compressed felt wrapped around it. The outermost layer of felt is called the hammer felt or strike felt — it is the surface that makes contact with the string. The felt is compressed in tightly controlled layers during manufacture, with specific density gradients from core to surface.
Hammer size varies across the keyboard — treble hammers are small and light (as little as 5g), bass hammers are larger and heavier. This mass graduation helps the pianist control dynamics uniformly across the keyboard.
When a hammer strikes a string, the contact duration and contact force profile determine the harmonic content of the resulting sound. A soft hammer makes longer, gentler contact — it excites fewer high harmonics and produces a warm, rounded tone. A hard hammer makes briefer, sharper contact — it excites more high harmonics and produces a bright, penetrating tone.
This is why hammer felt density is the primary tonal control in piano design. Manufacturers carefully engineer the felt density and compression for each instrument's intended tone character. Premium European concert pianos use different felt formulations than more affordable Japanese home pianos.
Every time a hammer strikes a string, the string cuts slightly into the hammer felt surface. Over thousands of strikes, one or two grooves form at the exact point of string contact. In the treble (where three strings contact one hammer), three parallel grooves develop. These grooves create a flat, hard surface at the contact zone — the hammer now makes sharp, metallic contact instead of the rounded contact of new felt.
Result: tone becomes progressively brighter and harsher over years of use.
Hammer felt is compressed wool. In Singapore's 70–90% humidity, felt absorbs atmospheric moisture and softens. Softened felt produces warmer, rounder tone initially. However, as humidity cycles — particularly when a room is sometimes air-conditioned and sometimes not — the felt repeatedly absorbs and releases moisture. Each cycle compresses the felt fibres slightly more. Over years, the felt becomes harder and more grooved than it would be in a stable climate. The pattern in Singapore is that pianos can sound acceptable in the humid season and harsh in the more climate-controlled season as the felt reacts differently to ambient moisture.
Voicing is the craft of adjusting hammer felt density and surface to achieve a desired tone quality. There are two primary voicing techniques:
Fine steel needles are inserted into the hammer felt at specific points and depths. Needling breaks compressed felt fibres and makes them less dense. The result: the hammer makes softer, longer contact with the string — warmer, more rounded tone. This is the most common voicing intervention, especially in Singapore where long-term humidity hardening produces an increasingly bright tone.
The surface of worn hammers can be lightly sanded to restore contact geometry, or a chemical hardener applied to restore density. This is less common in Singapore (where tone is more often too bright than too soft) but is used after hammer replacement to achieve desired brightness from new, soft hammers.
| Hammer Condition | Solution | Cost |
|---|---|---|
| Bright tone, surface hardening, shallow grooves | Voicing (needling) | S$120–S$350 |
| Moderate grooves, felt still substantial | Surface filing + voicing | S$150–S$400 |
| Deep grooves (2–3mm) through felt to core | Hammer replacement | S$600–S$1,200 |
| Felt hardened throughout, no needle response | Hammer replacement | S$600–S$1,200 |
| Hammer shanks broken | Individual shank/hammer replacement | S$30–S$80 each |
New hammers have virgin, soft felt. They typically sound too bright (or too soft, depending on how new felt interacts with the piano's strings and soundboard). A break-in period of 2–4 weeks of regular playing is needed, followed by initial voicing to refine the tone. Full tonal stability comes after 3–6 months of use. The action also needs full regulation after new hammer installation because the new hammer geometry changes every regulated dimension.
We assess hammer condition and advise whether voicing or replacement is needed — honest, accurate diagnosis.
Voicing from S$120. Full hammer replacement S$600–S$1,200. Islandwide service.