Music Theory: Key of D (two sharps)

So far, we’ve learned about the key of C and its Major Scale…

…the key of G and its Major Scale…

Now, let’s build the D Major Scale. But let’s first see if we can notice any patterns when we built the G Major Scale.

Perhaps you noticed that G is a 5th from C. Count it out: C-D-E-F-G…1, 2, 3, 4, 5.

Similarly, D is a 5th from G. Count it out: G-A-B-C-D…1, 2, 3, 4, 5.

If “going” from C to G meant that we need to add 1 sharp to our key signature, does that mean we’ll need to add another sharp when building the D Major Scale?

• C has no sharps (or flats).
• G has 1 sharp.
• Therefore, D must have 2 sharps? Let’s check…

In the above graphic, the 3rd labeled note is F♮(natural) and the 4th labeled note is G♮(natural). But they are separated by an unnamed note (ie. a whole step apart). The 221-2221 formula tells us that we need the note that is in-between those two notes. We’ll call it F♯ (sharp). And we’ll put F♮(natural) away and let it become a black note that is not part of the scale.

Next, you’ll also notice that C and D are a whole step apart (ie. separated by an unnamed note). Again, the 221-2221 formula tells us that we need to use the note in-between C♮(natural) and D♮(natural). Let’s call it C♯. We’ll then put C♮(natural) away and let it become a black note that is not part of the scale.

So, yes the pattern fits! The key of D has two sharps.

Notice what happened: the key of D kept the F♯ from the key of G and added just one new sharp, C♯. That’s the pattern. Each time you go up a 5th to a new key, you keep the sharps you already had and add exactly one more.

And that new sharp is always the 7th note of the new scale, a half step below the tonic. F♯ is the 7th note of G Major, and C♯ is the 7th note of D Major.