I believe you're running into another version of the same problem I describe here:
To put it simply, each script block has its own namespace, so the 'MyStreaming' variable isn't exactly destroyed - it simply cannot be accessed outside the block where it was created.
What you'd do in your example is instead of declaring your stream using 'var myStreaming =', declare it like 'window.myStreaming =' - the window object will be accessible from your other block, and thus 'window.myStreaming.stop()' should hopefully work. Good luck!
Thanks, it is true that windows works to keep variables from one block to another, but there is something that my code is missing, an id to identify the audio that has been played, since I can not even stop the audio within the same block.