Thread blocking problem

[Garyr]

I have a program consisting primarily of a simple Tinker GUI and in separate
thread some code that invokes a function in a C++ extension module that
blocks on WaitForSingleObject most of the time. The Python code is a
producer and the C++ code the consumer, a sound card driver.

Shouldn't the GUI be responsive when the code in the thread is blocked?

In this program it appears that processing outside of the thread occurs only
when the code in the thread executes briefly. That is, whenever the sound
card accepts another chunk of data. If I comment the function call that
passes
the data to the sound card and stick in a delay processing appears to be
normal.

The sound card driver (which I did not write) worked very well in the C++
program that I got if from

Does anyone have any thoughts on what might be going on here?