I am almost finished with my M. Schulz upright pneumatics.  I would
like to somehow soften the hammer felt.  The felt is very hard and
gives a slight tinny sound.

My tuner softened them up a little using a sewing machine needle
connected to a cordless Dremel tool.  He said that fabric softener
could be used but you must be very careful.  I didn't press him for
more info on this technique.

The best solution would be to replace the hammers, but this is
currently beyond both my expertise and wallet.  Some day I will
re-condition the piano mechanism (lots of homework to do first).

Thanks,
Jeff Lofton