In reply to Jon Stewart:
Depends how much of a hassle a 'ball-ache' is?
Download a free 'You-tube' download programme eg. YTD Youtube Downloader
Download a free Convert video programme eg. Freemake Video converter
and use the second to convert your video file into an MP3, ie it just takes the audio data out and leaves the video behind.
Both programmes have their uses above and beyond this one application so are useful to have,
Just be careful of all the 'free' add-ons that a 'free' downloads brings with it.
ALTERNATIVELY; download a audio recoeding programme that records into MP3 from your soundcard eg. "Audio recorder for free"
and just play the video on Youtube and press start/stop where-ever needed.
I'm not an expert at this sort of stuff, but both methods work for me.