The key of E Major is a bright and cheerful key, full of joy and optimism. It's the most popular key in popular music, with the tonic note being E and its relative minor key being C# minor. It's built on the Ionian scale, which uses the notes E-F#-G#-A-B-C#-D#-E. This key is often used for upbeat pop and rock music, as well as in many songs from the classical repertoire.