If you start
playing from the note F, and play eight notes, that
is the scale of F major.
F
G
A
B flat C
D
E
F
Click the play arrow twice.
At the beginning of this, you will see the key signature with one flat,
indicating that in this piece of music all the B notes are flats. Instead
of the white note B, you play the black note B flat. The B flats just to the
left of the B notes.