add a freesound object to allow to search for sounds on freesound.org
freesound.org is a good sources of free sound.
kdenlive has already defined a class which send a request to the freesound website and display the results in a Qt window. The source code is located in kdenlive/src/utils -> freesound.h + freesound.cpp.
This class seems to be lightly connected to kde and kdenlive and could be easily merged into qtractor.