Just to warn people there is a band called Beck, and has nothing to do with this anime, which is reason why in the anime they have a second name "Mongolian Chop Squad".
I watched this anime a year or two ago, and it's all most that good you might want to pick up a guitar and learn how to play it.
>>3 there is also some stuff on youtube - English dub one -
Moon on the Water -
https://www.youtube.com/watch?v=_BBvMwFH3Vg
Slip Out -
https://www.youtube.com/watch?v=WN2etQ7XDkM