Riddle for the Weekend

[A440A@aol.com]

Greetings all,

      I just wasted an hour finding this,  go figure...........

      The artist tells me that she hears a metallic noise, on release, but
only with the middle Bb chord,  both hands, and only at piano level or
softer.  It only does it when the pedal is also being released as her hands
are coming off the keys.

    I listen, I hear.  It sounds like a metallic overtone from a back string.
 It only does it at the end of a particular passage.

The piano is a Steinway M, #261261

      When I finally found the problem, it was nothing to do with the
strings, plate,case, or wheels,  it was not to be found in any of the keys,
whippens, hammer shanks, damper underlevers action rails, sostenuto or
keyframe. It was not some exterior object rattling along with the piano.  I
had had my hand on the offending item twice during the investigation, and
then only by chance did it occur to me what it was.
    the repair took  twenty seconds to effect, and 20 minutes to dry.

Guesses??????

( I only posted this because several replies following the last riddle
suggested an interest,   I think this is kinda an easy one compared to the
spring-tail bending)

Regards to all
Ed Foote
Precision Piano Works
Nashville, Tn.