Here's the info on the ED.

Don't Say "Lazy"
PCCG-70038
released 2009.04.22
1260 yen

This CD contains the ending song to the TV anime K-On (けいおん！).

The tracks are as follows.

   1. Don't Say "Lazy"
   2. Sweet Bitter Beauty Song
   3. Don't Say "Lazy" (Instrumental)
   4. Sweet Bitter Beauty Song (Instrumental) 

Songs by the Sakura Kou Keionbu (桜高軽音部)
[Hirasawa Yui, Akiyama Mio, Tainaka Ritsu, Kotobuki Tsumugi],
voice by Toyosaki Aki (豊崎愛生), Hikasa Youko (日笠陽子),
Satou Satomi (佐藤聡美), Kotobuki Minako (寿美菜子).
Main vocal by Hikasa Youko.

The first press of this CD package contains individual CD
jackets of the girls. 

Web page at (images of the individual jackets)

http://www.usagi.org/doi/seiyuu/cd/toyosaki/dont-say-lazy.html

--
Hitoshi Doi
                         " this space for rent "
http://www.usagi.org/doi/                                    doi@usagi.org