I have noticed that a couple of hammers on my 100 year old upright remain touching the strings once they have stuck them (that is, if the key or the sustain pedal remains depressed) resulting in a heavily muted, dull thudding sound.

The tech who visited today to tune the piano (and lubricate the hammer pins) did not remedy the thud problem.

Could anybody advise on what I should do?

The situation you refer to is called blocking. It is an adjustment problem. The key may go down too deep, the catcher may not be correct, or the let-off is incorrect, or a combination of these. In addition, the action parts in your piano being 100 years old, may be too worn to adjust properly. The hammer return springs could be weak. There should have been something your tech could have done to fix the blocking. Try calling him back.

[ November 06, 2001: Message edited by: Bob ]