Glides and after touch

[RobertD429@aol.com]

>Subj:      Re: Glides and after touch
>Date:      96-03-06 12:02:00 EST
>From:      GerryLisa@aol.com

>Setting the glide buttons to a position higher than what they are intended
>will only make the keyframe "rock".  Those "experienced" technicians should
>know better.
-----------------------------
"Experienced" technicians know that there is a place for many non-standard
procedures, as long as it is acknowledged that a tradeoff is being made. I
think Bob Bussell's question implied that he knew it was a departure from
standard practice to lower gliders (raising the balance rail) for increased
aftertouch. If the piano was "perfectly" regulated to begin with, the need
for aftertouch adjustment usually comes from a sagging hammer line (from
compression of cushioning materials), and the most direct solution is to
raise the hammers to their original positions.

However, as an example, assume the technician is doing concert prep on a
piano and is under extreme time pressure (it happens). The pianist requires
more aftertouch either because of preference or because the aforementioned
sagging hammer line won't allow letoff. Lowering the gliders a SMALL amount
can get that aftertouch on a temporary basis by raising the balance rail. The
price is increased friction on the shift. Too much and the action can get
stuck in the shifted position or be slow to return, as well as being
difficult to operate. The amount of adjustment is also limited by its effect
on other aspects of the regulation -- the hammers can rise too close to the
strings after drop, the checking distance will change, the repetition springs
will behave differently, etc. On the next visit the technician can return
things to the desired configuration. Gliders are not the primary adjustment
for aftertouch; I'm just making the point that sometimes not going by the
book can get the job done, as long as we are aware of  ALL the effects.

The opposite adjustment is not valid; the gliders can not be withdrawn to
decrease aftertouch unless they were already too tight, because the balance
rail will knock and the action will feel spongy.

Incidentally, if the keyframe rocks, it probably isn't properly fitted at the
blocks and dags. Some manufacturers even specify a little pressure on the
gliders to make sure the action stays "glued" to the keybed under all
conditions. On the other hand, if the gliders are REALLY cranked excessively,
the front rail can lift slightly off the keybed and knock.

Bob Davis
University of the Pacific
Stockton, CA