Originally Posted by: jwm3320Let's take the an example of 12 bar blues in key of A. The I, IV, V chord usually played is A7, D7, and E7 respectively, and many things I read say you should solo/improvise over the 12 bar blues using A minor pentatonic, but the key is in A major. Why wouldn't A major pentatonic be a better choice. Also, why do they often play the I and IV chord as a dominant 7 chord vs a major 7 chord?

Hey, Joseph. In addition to Mike's excellent answer, I have a few tutorials aimed exactly at your question. This one in particular covers how & why mixing major & minor notes is a key characteristic of the blues.

https://www.guitartricks.com/tutorial.php?input=217

Hope that helps!