How this circuit works?

Hello
I have the following questions, can anyone explain to me how the
following circuit works, how does the first op-amp oscillate, and how
does the buzzer sound?

The first op-amp is configured with negative feedback, which normally
means that the negative input will try to equal the positive input,
which is always at half vdd, therefore it is unclear why it would
oscillate.

Secondly, the 2nd op-amp is connected to a dc level, so how would we
hear the piezo, which needs an ac signal to be heard?

The circuit is here

http://www.geocities.com/maxcotester/S5030995.jpg
http://www.geocities.com/maxcotester/S5030996.jpg
http://www.geocities.com/maxcotester/S5030997.jpg