The ability to understand, diagnose, and implement the work necessary to put a piano in its maximum playing condition, and keep it there, through judicious maintenance, throughout its years of use.

Once a piano is brought to a high level of performance through rounds of tuning, action regulation and tone building (which includes voicing) it requires relatively little maintenance to keep it at the same high level of function year after year.  Naturally, the amount of maintenance needed varies with the amount and intensity of usage.