To expand a little on what Joey said, a scale is a sort of conglomerate of
all the notes used. It does not tell you how the notes are used.
Most advanced players tend to think in terms of chords rather than scales
with scales being only the glue that keeps them on the right track.
In blues, the I IV and V of a major key are played as dominants BUT the
melodies tend to chose notes from the minor scale built on the same root.
This is the style of blues. To make it work though it is not enough simply
to play the scale but you have to play in the blues idiom.
To contrast, country music tends to use the same progressions in the same
way(in many cases at least) yet has a totally different style. How can this
be? Specially when the scales are almost identical?
In C blues the Cm pentatonic is used with the added blues notes:
C Eb F Gb G Bb C
In country the Cmaj pentatonic is used
C D E G A Bb C
But in both cases the combined scale, which is C mixolydian with the added
b3rd and b5th are used. The scales are almost identical but the emphasis on
the intervals are much more different.
The best way to make this clear is to simply realize that the chromatic
scale covers ALL possibilities neglecting microtonal variations.What this
means is some notes become more important that others.
But before we oversimplify it you have to realize that the emphasis changes
depending on which chord is being played. A good player will think
differently over an E7 chord than an A7 chord in some key. Over the E7 chord
the D will be very important in blues and country but over the A7 chord the
D will be deemphasized by most players. Why is does this happen? Because
most musicians think in terms of chords/harmonies rather than scales.
A scale is just a group of notes that you can draw from and be reasonably
assured they will work more or less. A scale does not tell you which notes
are the best notes to play at any instant. Sometimes the best note to play,
if there is such a note, is not even in the scale. Other times the best note
to play is not even a chord time.
In your example you have a E blues(note it is not E major but E blues!!!
They are different). The Emin pentatonic gets all the main notes to get that
blues sound. But playing random notes from that scale won't work. Even
playing the right notes with the wrong feel won't work. You have to play in
the proper idiom.
An analogy is speaking a foreign language. It is not enough to know the
vocabulary. If you want to be completely fluent in it you have to also have
the mannerisms, vocal inflections, etc. Without these people will recognize
something is different, usually for the worse.
As far as chord naming goes, it can be quite difficult to explain quickly.
But for the most part the major scale is used as a template and the major
chord is the basis. Tonal music is built off 3rds(basically skipping 2 or 3
notes on a piano or 1 note on the white keys).
We somehow we've determine the "root" of a chord is C then if we write the C
major scale in 3rds we have
C E G B D F A
This is the template for our chord. It is a Cmaj13 chord. When we add or
subtract notes the chord changes. The 13 comes from the highest interval in
the chord using that pattern above. 13 = 6 = A.
Suppose we turn the B into a Bb. We now have a dominant type of chord and we
would label it as C13.
If we leave off the last 3 notes we have a C7 = C E G Bb (....)
If we add notes outside the scale it becomes more trickly. If we play a
C#/Db along with the C7 chord we would label it as a C7b9. With experience
you will recognize this exactly as the notes C E G Bb Db(not necessarily in
that order).
For your E blues you start with an E7 chord. When you play a G note from the
E blues scale over it the you end up with both a major and minor 3rd in the
harmony. Since we have no way to specify both a major and minor 3rd we
actually treat the G as a F##. F## in the key of E is an augmented 2nd(since
F# is the major 2nd).
So the E7 chord with a G being played on top of it would be written as E7#9.
This just means we have an E7 chord with a G in it somewhere. It sounds
bluesy because it exactly is. It contains both the major 3rd and the minor
3rd(or augmented 2nd).
If all this is very confusing you need to start with the very basics of
learning the theory of intervals and scales. Chord naming depends a great
deal on knowing your intervals. After all, a chord symbol is just trying to
tell us the intervals used. E7 tells me the exact notes I am suppose to be
playing. E7 = E G# B D. E7add9 should be obvious. It's an E7 chord with the
9th added. It's also known as E9(the add is redundant in this case). E7sus =
E7 with an A added. We could have written it as E11(no 9th) or even
E11(which contains the 9th but doesn't matter if it does or doesn't that
much) or E7add11.
Chord symbols is part science and part art. When you spend some type
learning the basic theory then get your fingers dirty with experience it all
starts to make sense.
In any case your original problem seems to be just realizing it is a blues
progression. That alone tells you a lot. When something is the blues it
almost always is the 12-bar blues which is a fixed progression of I7 - - -
IV7 - I7 - V7 IV7 I7 V7. The melody almost always comes from the minor
scale of the tonic.
If your having trouble following just look up 12-bar blues online and
memorize the progression(there are some slight differences). Memorize it,
practice it every day. Learn some blues licks and practice them. Forget
learning the theory until you have some foundation to work off.
If can be very difficult to learn something without context. Remember two
things: Theory followed practice AND most of the great musicians did not
know any theory(or rather they had an subconscious understanding of it).