When you play a chord progression how do you know what pentatonic blues or pentatonic to solo over it with? I know you use the one that sounds right but is their theory? Like one song is in F#m (or Amaj). The I chord s Amaj so I guess that means it is in Amajor?? But, I can solo in only A pentatonic or F#pentatonic blues. I know it doesn't, but shouldn't Amaj Pentatonic Blues work because its in A? Or is it in F#???!!! Ahhh! Help me!
You need to provide more information -- what is the chord progression? In general, most blues is in I-IV-V-I form of some sort... if the I is A Major, the A Major pentatonic is probably appropriate, but don't get too bogged down in scales, especially scales as limiting as a pentatonic scale. I've played blues for a long, long time, and yes, Western theory can be applied to blues, but I don't think about theory at all when I'm soloing (I play more blues guitar than I do blues piano, by the way, not that it really makes a difference). You gotta just play a buttload until you get the feel for it. Blues is blues. Scales in blues are just skeletons or reference points, nothing more. Knowing your intervals is more important than knowing your scales, really (for blues, at least). Know your intervals and know your instrument.
With that aside...
If you know what the chord progression is, "safe" notes when soloing will always be any note in the chord. So if the chord progression is A - D - E - A (I-IV-V-I), then during the A chords, the "safe notes" will be A, C#, and E. During the D chord, the "safe notes" will be D, F#, and A. During the E chord, the "safe notes" will be E, G#, and B. Flat 7ths are often "safe notes" too (obviously -- this is blues). But you probably don't want to be too safe, anyway. Rules are meant to be broken in blues and rock.
Also, always know the MELODY of the piece you're playing. Some of the best solos are just embellishments on the song's melody -- and if you can play the melody, you always have something to fall back on if you get stuck in a rut or something.
This advice is just basic stuff. Just play a lot (as in every waking hour) and you'll figure out what sounds good. That's really what blues and rock soloing is about: using your ear. Basic knowledge of theory is obviously preferrable, but that basic knowledge should become second nature so that you're not thinking about it as you're playing. Play from the soul, broseph. THE SOUL, DAMMIT!
ROCK!!!
Peace,
Mike