Seems like it, which is why I think the Csus2 was actually the right call.
I'm way better at theory than I am at the fretboard, but knowing theory has made learning the fretboard way easier, and made me a much better player.
Anyway, there are some oddities with extended chords (the 7s, and 9s and 11s and 13s). They are really "jazz" chords, and we all know those jazz guys are always a bit off. <img src="images/smiley_icons/icon_biggrin.gif" border=0 alt="Very Happy"> For the most part, the number indicates which note of the scale you'd add to the chord, but there are some caveats.
If you play any blues, you play 7 chords. Given the explanation before, it would seem that a C7 would mean you add a B to the chord, but that's not the case. 7 chords are also known as "dominant" 7s, and you really add a flattened 7th (Bb in the case of a C7) so it's different. A straight up 7 chord as I described above would be a "major 7" indicating you're staying true to the major scale. So if you see that in a chord chart, that's what it means. It took me a while to get the difference between a maj7 and a 7 chord, as the descriptions are backwards. It makes more sense to call the dom7 a "flat7" chord and the "maj7" the 7 chord. But I don't make the rules.
<img src="images/smiley_icons/icon_biggrin.gif" border=0 alt="Very Happy">
So anyway, in the case of a D2, we can break it down like this.
D major scale
1 2 3 4 5 6 7
D E F# G A B C#
So D major is D F# A.
If it's a sus2, you'd use E instead of F# and if it's a straight up D2, then you'd add the E inclusive of the F#.
I guess if I was going to stress any one thing, it's learn the major scales. The entirety of western music is based on them. All your chords are derived from scales. All your modes are derived from scales. The beauty is that they aren't really all that complicated.
Someday we'll win this thing...
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