Although I have never constructed a pneumatically operated xylophone,
I have constructed MIDI-controlled, solenoid actuated glockenspiels
and a xylophone.

The hammer (wood, in my case) must not remain in contact with the bar,
otherwise a buzzing noise will result and the tone will not sing out.
As Robbie mentioned, the resilience of the shank or action allows the
hammer to reach the bar and then bounce off the bar and remain at about
1/8" from it on non-reiterating units.

Robbie commented, "The marimba is a xylophone with a small buzzer in
the resonator."

I agree with Robbie that a glockenspiel is of metal bars and a
xylophone is of wood (rosewood, perhaps) bars.  But, Robbie, I have
to differ with this: I believe a marimba is a xylophone with tuned tube
resonators below the bar.  What do you mean by "small buzzer"?

(Plans for building a marimba from an old article are located at:
http://msnhomepages.talkcity.com/cookingct/italiano34/marimbaarticle.html)

And to go further: A Vibraphone is a metal glockenspiel played
horizontally just like a marimba.  It also has tuned tube resonators
with the addition of "butterfly" valves at the entrance to the tubes.
These round plates are connected on one shaft and are rotated by an
electric motor when a foot pedal is pressed. This gives a pleasing
mellow vibrato (or is it tremulant?) effect.

When I go to eBay to look for glock bars or wooden xylophone bars,
I am amazed to find the mis-nomenclature used.  I think it all started
ages ago when the metal bar musical toys came out and the manufacturers
called them xylophones.

The organ industry and the nickelodeon industry may have different
names for these instruments.  So I don't mind being corrected if that
is the case.

Andy LaTorre
Sylva, NC

 [ Xylophones used in orchestras usually have resonator tubes for more
 [ volume, but in orchestrions they're usually without.  The marimba of
 [ Central America, which is the one commonly heard in recordings, has
 [ a little buzzer (like a Kazoo!) installed in the bottom of the
 [ resonator.  Without the buzzer the instrument would be simply a big
 [ xylophone.  The xylophone is an ancient instrument; the name "marimba"
 [ comes from Africa.
 [
 [ J.C. Deagan was a pioneer applying hard aluminum to his musical
 [ instruments.  "Vibraphone" is a Deagan trade name and thus should
 [ be capitalized.  Glockenspiel is the German word adopted in English,
 [ and so capitalization is optional.   -- Robbie