beamer wrote:If the key of the song is based on the first chord played, as I understand it, . . .
The key of the song is OFTEN the first chord played, but not always. A good example is "Mr. Jones" by Counting Crows. It's in the key of C, but you don't hear the first C until the chorus starts. (The verse is Am - F - Dm - G - Am - F - G - G, and the chorus is C - F - G.)
beamer wrote:. . . what key is D Am7 Em? I always asumed it was a D progression and so have been trying some leed in the D major pentatonic. Is this still right?
You may be right, I don't know. With those chords and depending on the order it could also be variants of A or E.
If you really want to know, I suggest you post this question in the theory section where Jerome, Russ or one of the experts are more likely to see it.
"Just because you've always done it that way doesn't mean it's not incredibly stupid." - Despair, Inc.