The Tallis Scholars
The Tallis Scholars are a British vocal ensemble normally consisting of 10 members.
Official website: http://www.thetallisscholars.co.uk/
Formed in 1973 by their director Peter Phillips, they specialize in performing a cappella sacred vocal music written during the Renaissance by composers from all over Europe.
They are currently recognized as one of the world leaders in this field, having risen to a place of prominence among other professional ensembles.