When a Flat sign is placed in front of a note, it means that we must play the key immediately to it's left. I will explain this more fully, but first, here is what the flat sign looks like.
As an example, let's look at the note 'B flat' to the left of Middle C.
This is the black key, in between A and B in the blue section of your keyboard template
When B flat is written in music notation, it looks like this:
And here is the note B Flat on the keyboard
The first chord that we shall look at, which has a B flat in it, is the chord, C7. (played with the left hand. Finger numbers shown)
Click the audio button to hear this chord
In the next lesson, I shall demonstrate two new chords, F major (root position), and B flat major (second inversion) which together with the C7 chord, will enable you to play music written in the key of F major. More about this later.