Originally Posted by: hdoranI am trying to soak up all I can on music theory and have one question about which notes are in a certain key.[/quote]
If you haven't already, I encourage you to go through Guitar Fundamentals 2, which starts with a primer on music theory.
http://www.guitartricks.com/course.php?input=2
Next, this tutorial covers the basics of music theory. It will show you how to determine notes in a key. Further, it shows you how to build the chords that are related to each key. Then you can determine which chords are part of a scale. This is called triadic harmony.
http://www.guitartricks.com/tutorial.php?input=495
When you are ready to get more in depth, this tutorial covers the circle of fifths. It will show you the notes that comprise each of the 12 possible major keys, one key at a time.
http://www.guitartricks.com/tutorial.php?input=835
Now, to answer your specific question.
[QUOTE=hdoran]
To illustrate, suppose we are in the key of C major, which obviously includes:
C - D - E - F - G - A - B
My question is whether variants of those notes are also in the key of C. So, for example, is an E dominant 7 in the key of C (since an E major is). Or, is an A-minor also in the key of C.
The terms scale and key mean virtually the same thing. However, the scale is only the notes:
C - D - E - F - G - A - B
What you can do with them (mix them into chords, etc.) & how they relate to each other is the key of C major.
Next, E dominant 7 is a chord, which is made of 4 notes. So, what you want to know is, "Are all the notes in the E7 chord also in the C major scale or key?"
Here are the notes of E7:
E (1st) - G-sharp (major 3rd) - B (5th) - D (minor 7th)
Since E7 contains the note G-sharp, it is not in the key of C major (all of the notes of the E7 are not contained in the C major scale).
Here are the notes of an A minor chord:
A (1st) - C (minor 3rd) - E (5th)
Since all of the notes of an A minor chord are found in the C major scale, it is in the key of C major. It is the sixth chord; written as a lower case Roman Numeral (vi). This info is covered in depth in the music theory tutorial linked above.
Hope this helps! Let me know if you have any other theory questions. Have fun. :)
