There are at least two bands with the name kei:

1. Hayashikei (ハヤシケイ) also known as Eshinajai-KEI (絵師じゃない) better known as KEI is japanese vocaloid music producer who have created a number of works using Hatsune Miku, Megurine Luka, and VY1. KEI's most notable work is Tower; which is his first work to enter the Nico Hall of Fame. Note that he has no connections whatsoever with the illustrator KEI.
He has earned the title "Legendary VY1 Master" in several of his works such as "ARIGATO" and "Doomsday Clock".

Additionally he is trying to sing: http://youtu.be/gdZkP51QKcQ

Discography:

Echo Echo Me - 23 january 2010
Heliocentrism - 16 january 2011
Horror for holiday shoppers - 12 juny 2011
Universe and Stupidity - 29 april 2012.

Most famous works:
"Starship" (Miku) (Feb.21.2008)
"Full Swing" (Rin) (Mar.16.2008)
"Present" (Len) (Apr.02.2008)
"Reverse Day" (Miku) (Jul.18.2008)
"Moment" (Miku) (Dec.11.2008)
"Flurry" (Miku) (Jan.08.2009)
"Utopia" (Miku) (May.08.2009)
"Tower" (Luka) (Jun.08.2009) with subtitles
"Firefly" (Miku) (Aug.24.2009)
"Putting Aside, Thinking Aloud" (Luka) (Oct.12.2009) with subtitles
"Mayday" (Miku) (Mar.04.2010)
"Echo" (Miku) (May.05.2010)
"Pierrot" (Miku) (Jun.29.2010)
"Jack" (Miku) (Nov.02.2010)
"I Love You, I Need You" (Miku) (Jan.03.2011)
"Invitation" (VY1) (Mar.31.2011) with subtitles
"Handwritten Map" (VY1) (May.09.2011) with subtitles
"Neverland" (VY1) (May.16.2011) with subtitles
"Doomsday Clock" (VY1) (May.23.2011) with subtitles
"ARIGATO" (VY1) (May.30.2011)
"HERE" (Miku) (Jul.06.2011)
"Hello,Worker" (Luka) (Sep.02.2011) with subtitles
"Track" (Luka)(Nov.03.2011)
"I've Been Lost" (Gumi)(Mar.23.2012) with subtitles

Official blog: http://homingecho.blog84.fc2.com/
PIAPRO: http://piapro.jp/kei0111
Twitter: https://twitter.com/#!/homing_echo
Nico nico douga: http://www.nicovideo.jp/user/334765
Youtube: http://www.youtube.com/user/HomingEcho


2. KEi (Bulgarian: КЕй) is a DJ and producer from Sofia, Bulgaria. He is part of the pbpm collective. www.pbpm.net.

3. Kei Hamada (Japanese: 濱田圭) born in Zama City, Kanagawa, Japan on August 12th 1984, is an artist, composer and guitarist. He is most known as the guitarist of kannivalism and disbanded baroque.

kei (圭) started his solo career in September 2008, and announced shortly after, that his debut single, titled "the primary." will be released on November 19th 2008.

In January 14th 2009, his second single "vesperbell." was released in two editions.

One week before the release of "vesperbell.", kei (圭) announced on his homepage, that his first album titled "silk tree." will be released on March 4th 2009 in three editions.

Official homepage: http://www.kei-hmd.com

4. Kei is recording artist and producer from Serbia. He has one released mixtape Minut (2016) under Bassivity Digital. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.