recording experiment

[Stéphane Collin]

Hello list.

I just bought some chinese microphones (very good) and did some recording 
tests on my piano.
One thing was obvious : when you put cardioid microphones close to a piano, 
it takes what is in front of it and nothing of what is at sides or behind.
So, putting two cardioid microphones in the opening of the lid at, say, 50 
cm of the soundboard gives you a nice sound, but with this setting, high 
trebble or low bass are not so present, because not in front of the 
microphone.
Some recording tech told me : just put your mics 5 cm from the bridges, and 
they will take all the scale.
Indeed, this is so.  When you put the mics very close to the bridge, they 
take all of the scale.  This seems to be very well known among recording 
techs.
So I thought : why is that ?  The only response I could imagine is this : 
the bridge itself carries all of the vibrations of all strings bearing on it 
equally.  It is the soundboard that reacts, with it's different dimensions 
from trebble to bass, to the appropriate frequencies of the strings.
Any thoughts ? (sorry for my limit english).

Best regards.

Stéphane Collin.