There are more than one Band that called themselves COY.
Most know are the swedish Coy, with the following description.
Take a singer/pianist with a voice somewhere between Alanis and Tori Amos, who writes songs with crystal clear messages with a substance to a world of listeners that are fed up with decades of tiring pop music consisting of dumbing, blah-blah “Baby, I love you”-lyrics and overused chord progressions. Add a bass player who is the most steady, reliable and groovy a bass player can be, and who is one of the few that would make Tony Levin envious. Throw in a guitarist who is the only next logical step after David Rhodes (with Peter Gabriel) and The Edge, and who also owns all of Pat Metheny´s records. Top it off with the only Swedish drummer who understood to pick the best out of the drumming of Carter Beauford, Manu Katché and Vinnie Colaiuta, and then turn it into something totally new and unique. What you get is COY, the most american-sounding band ever to be heard from the European continent!

Formed in 1999 by singer/pianist/songwriter Nejra Besic, the band has been through a few different line-ups, and has now finally found the ultimate combo. Together with Micke Karlsson, Jonatan Tjäder and Olle Prim backing the songs up with relentless power, pride and confidence, Nejra gets her message through to every new listener that meets COY, on stage or on record. COY is on the one hand the ultimate studio group who knows how to sound the best any band can sound on record. At the same time, they´re the most energetic, groovy and powerful live act to be seen since....well, since the best live concert you´ve been to so far!
With a new smokin´ set of eight marvellous songs, soon to be released on Swedish indie label Sally Productions, COY are more than prepared to tour the world (and beyond), spreading the message for everyone to hear: COY are here to stay! You could be one of those who were there from the beginning!

Nejra Besic: Vocals, piano and keyboards
Mikael Karlsson: Guitars and backing vocals
Jonatan Tjäder: Bass and backing vocals
Olle Prim: Drums and percussion

But there also was the German Band Coy from the Black Forest, which existed from 1995-2003.
There music style was a kind of alternative garage rock.
Mostly they were influenced by such acts like Nirvana, The Hellacopters, Monster Magnet, Cellophane Suckers and Fu Manchu.
Coy only released a 4-track Demo CD in 2003 and had a more or less big influence on their local music scene in Pforzheim,Calw, Stuttgart and Karlsruhe.

Bandmembers were:
Nedzad Pekusic - guitar/vocals
Ursula (Ouzo) Raschke - bass
Marcel(March)Wölfling - guitar/backing vocals
Manuel Madaric - drums
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Another artist named COY ist a young rock singer from Graz, Austria who won the local band contest in 2010 and just released her first single "Butterfly". Her influences are, for example, Anouk, Janis Joplin and Melissa Etheridge.
Links: http://www.coy-music.com and http://www.youtube.com/user/Coymusic