Gregorian chant may not be too exciting but it dates from much earlier than 1550. If you don't mind religious music there is some great stuff out there - mainly choral - some of it is mind-blowingly beautiful and difficult - try Spem in Alium by Tallis - a 40 part motet! Also look out for William Byrd and William Cornysh. Look out for a group called the Tallis Scholars - the best early music group in the world. They also do some secular pieces.