E minor

E minor (Em, Mim) is a minor scale based on the note E. Its key signature has one sharp, F Its relative major is G major.
A lot of classical guitar music is in E minor, because this key is very suited for the instrument. When it is tuned normally, four of the instrument's six strings are part of the tonic chord. The key is also very popular in heavy metal music, because the lowest note on a guitar, E, can be used a lot.
E minor was one of the most-often used keys by Felix Mendelssohn. 
Famous classical music in this key.
See also: List of symphonies in E minor