When a key is pressed on the piano, it activates the piano action mechanism, propelling the piano hammers to strike the strings, generating vibrations that are then amplified by the soundboard. The hammers play a crucial role in determining the piano's timbre. Voicing, a process of manipulating the density and texture of the felt-covered hammers, is employed to alter a piano's tone.

Voicing typically involves needling the felt at specific points or applying chemicals to achieve the desired tone. Its primary objective is to ensure uniformity in tone and power across all keys. Additionally, voicing allows for customization to suit pianists' preferences, aiding in the attainment of specific tones depending on the performer's repertoire or musical styles.

The need for voicing arises mainly from continuous playing, which can compact the felt and result in a brighter tone with reduced resonance. Environmental factors such as humidity can also influence the aging rate of the hammers.