i have made (re-made and fixed and improved... ) a simple audio looper based on

awk
sox
mplayer

can be found here

http://www.cli-apps.org/content/show.php/lal+linux+audio+looper?content=102398

**don't use small file use 1 minute audio file

"USAGE : "inputfile" fadein fadeout timeparameter "outputname.wav" "

it can be usefull for kdenlive... :)