by Felix Mendelssohn
is most likely in the Key of A Major
Notes in A Major:
A, B, C#/Db, D, E, F#/Gb, G#/Ab
Chords in A Major:
A, Bm, C#m, D, E, F#m, G#dim
This key can also be known as F#/Gb minor.
When it's used as a minor key, the minor key note is stressed more than the major key note. The same notes and same chords still apply.