In one of Charlie Chan's movies, there was a case of a radio vacuum tube glass bulb that would explode when someone on the air would sing a high pitched note causing it to break. When it did, a noxious deadly gas would be emitted and kill the nearest person. Which movie was this? I remember a recording studio from which the on air radio show was conducted for murder.
Thanks.

I believe we just screened that one recently. "On The Docks" with Roland Winters

I believe that was the scarlet clue.

If you remember in CC in Eygpt, Mr. Barry was playing his violin and it reached a high pitch and broke a glass tube placed inside the violin by murderer. Tube emitted a poisoness gas killing Mr. Barry.