Replace your madplay binary with this script, and make it executable, in order to use mpg321 instead of madplay.

#!/usr/bin/python
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import sys
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import os
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os.system("killall mpg321");
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child = os.fork();
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if child!=0:
    os.system ("mpg321 \"" + sys.argv[4]+"\"")
    os.system( "kill "+str(child))
else:
    sys.stdin.read(1);
    os.system( "killall mpg321")
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