memblocks are a way of retrieving the data for sound/images and objects
understanding the way each piece of data is stored can help you make changes
a sound memblock could help change pitch
an image memblock you could get the color of a particular pixel
an object memblock might help you modify a vertex of an object
ofcourse there are other things that they can do its up to you as its just a way of processing
the data once you understand how its stored
this thread may help get you started
https://forum.thegamecreators.com/thread/222027
with examples of the above. if you want to modify sounds my Krazy Grandprix is easily enough
searched and will provide sound modifying. Also if your lucky enough to own the games pack 1
my night driving code has an example of building 3d objects with memblocks by using the block
command