Download Wavepad by typing it in google
Find a result at the 1st page with some sound desc.
Open it up
Find a .wav .mp3 or whatever and save that in a place
Then open that in wavepad and then what you got?
listen to a part you want to have it end at
go a few seconds pass and then cover the whole part you want kept
Find a button and look at it it says "Trim" if you move your mouse over
click that
Bravo.
Then, listen to it to see if not just undo.
Go to convert channels
Pick mono
It could be loud if you have a loud one already.
Go to save file "AS"
click through as a ogg vorbis and then when you're done put it in blockland/add-ons/music when you save it.