A delicate pianissimo passage becomes very difficult or impossible to play, and some keys may not sound at all if played very lightly. Aging of the piano's strings and structure also can diminish its tone. High ceilings or large adjoining rooms add resonance. Rugs and upholstered furniture soften tone and add warmth. You don't like the sound even after it has been tuned.
Tone varies radically from note to note.
The piano has lost its ability to play softly. Then, play a wide variety of music on it. Most voicing procedures are long-lasting, so give yourself some time to explore the sound of a new instrument before deciding to change it. How often voicing is needed depends upon the piano's usage and its intended audience. Pianos in concert halls and recording studios often receive minor refinement of the voicing before each performance.