The Blue Notes
Blues gets it's musical color from the use of what are called "Blue Notes". The major diatonic scale is the "white" notes of the European traditional music, but it is possible to drop any note ½ a tone and make it flat (sometimes called minor or diminished). Dropping notes down in the scale alter the feeling of the scale and can make it darker or sad sounding. This is what I mean by altering the color. Blues gets it's particular feel by switching back and forth between Major and Minor notes. This is the BLUE in BLUES.
Webster's defines Blue Note as
Main Entry: blue note
Etymology: from its frequent use in blues music
: a variable microtonal lowering of the third, seventh, and occasionally fifth degrees of the major scale.
The Flat Third
The third is the middle note in the I chord. By dropping this note ½ of a step, the I chord becomes minor. A minor chord is sad sounding like funeral music. Blues is not funeral music so we switch back and forth between happy (Major) and sad (minor). This is the color of the music. This is why we call it blues.
In cross harp the flat third is the first bend in the 3 hole draw.
One of the first bluesy things that you did on harp was to "wail" the 3 hole by bending it back and forth between the unbent draw and the bent draw. This is a signature blues sound and it comes from flatting and un-flatting the third.
When you play minor blues (Stormy Monday, etc.) in cross harp, you never hit the 3 hole draw unbent. When you play country blues or gospel, you might never bend the 3 hole draw. Delta and Chicago Blues will require you to contrast the bent and unbent 3 hole draw to get that dark bluesy sound within a major sounding melody.
The Flat Seventh
Don't forget that you play in three chords when you play Blues. When you play in the IV and V, it's like playing in another key. The flat third in the IV chord is not available to you in cross without an over-blow, but in the V chord, it is right out there as the 5 draw.
The flat third of the V is also the flat VII when you count up from the I chord (this math makes me dizzy). The flat VII is a very, very important. In European music, the VII is added for color as a transition note. In folk music it is often used to heighten the tension in a chord. Since the VII clashes with the I and sounds dissonant, the ear wants to resolve it to a nice clean chord like the major chord.
Blues is not a music that cares much about nice clean Major chords. If your guitar player is playing major chords or even Seventh chords, you should smack his fingers with a ruler and tell him to learn the Diminished 7 chords - these are the Blues chords. Diminished is the way guitar players call the chords with the flats in them. (You drop down ½ step - diminish - the VII note).
In minor blues, you hit the flat VII and let it wail. The 5 draw doesn't bend very much, only a ¼ tone, but wail it anyway, especially in minor blues.
I want to play as much of the flat 7 as I can fit into my music. I already have the 5 hole draw and I'll spend a lot of time there, wailing it, but the 5 hole can be shrill and piercing. This is a good thing, until you spend all night (as I see newbies doing) wailing the 5 and nothing else. You can play it lower down on the harp. A more important - probably the most important - blue note in cross position is the 2 hole draw bent all the way down.
You have to learn to bend the 2 hole down to the flat 7. This is the double
bend in the 2 hole. The first bend is the un-flattened 7 and sounds very European
folksy. Open up your glottis and pull down from the bottom of your lungs. You
can't do it right if you are sitting down. Charlie Sayles told me that a good
two hole draw feels like its coming from the bottom of your feet. You get that
deep church organ sound. The first few times that you do it, it vibrates your
lungs and tickles your innards so you have to laugh out loud.
Listen to Big Walter Horton. He can play a whole song dwelling mostly in that deep 2 draw well. (When I die, I want to be reincarnated as a tall, lanky, alcoholic black man who can play blues harp)
The flat 7 should be the starting point or ending point of many of your riffs. When you start out playing cross, you tend to seek the refuge of the unbent 2 draw or 3 blow because this is the tonic or I chord base. This note is always safe and is the natural resolution of the music. Safe, however, can be boring. You want to end a phrase with the beginning of the next phrase. By kicking off from the two flat 7 we add interest. By resolving to the flat 7, instead of the I, we spice things up. (hint: at the end of a blues song, instead of playing the 2 hole unbent as the last not, bend it down and end on that flat seven to give a cool jazzy ending to your performance.)
The Flat V.
Webster's said that the blue note refers sometimes to the flat V. In cross, the flat V is the 4 hole draw bent and the 1 hole draw bent. The V, of course is one of the three blues chords. Bending this own is useful for a transition to the IV chord. Start at the V, bend it to create tension, and resolve it to the IV. I use this on most every song. For example I play the 1 hole draw in the V chord and then bend it down to the flat V and resolve that into the 1 hole blow for the kick off note in a whatever riff I play in the IV chord. You can do the same in the 4 hole. You may ask - every song? I think the turn-around adds structure to the blues. The listener marks the beginning of a new verse through the turn-around and I feel it's good to be little less creative in defining the move into the turn-around so that the listener doesn't get lost. You are, after all, playing to an audience that has been drinking a lot of beer.
One thing that newbies do is to dwell on the 4 and 5 hole wails. If you find yourself doing this, you are not sounding very good. These are great notes, but get down and dirty and do something on the low end of the harp to make these notes an interesting surprise and not the meat of your performance. A much harder thing to do would be the 3 hole first bend with a riff leading down to the 2 hole double bend and then back up again.
Putting it all together.
If you lay the Blue Notes down on top of the diatonic scale you get a new scale. The Blues Scale is loosely defined by a 6-note scale (more or less), but depending on the style of blues, the notes vary. The scale is: I, flat III, IV, flat V, V, flat VII. This doesn't mean that you stop playing the un-flatted III or never play the VII or the II. Blues is not that easy. The Blues scale is a suggestion, not a law. The Blues scale notes are the BIG notes that make blues sound like blues, but you must play little notes or transition notes between the BIG notes. The blues scale notes are the notes that you emphasis. You can play blues exclusively in the notes of the Blues Scale, but you will bore your listeners before very long.
My advice is to practice the blues scale over and over until you can play any note clearly without having to search in a bend for the right sound. Use these notes as a base and then go and learn transitions in and out of this scale to add ornamentation to your riffs.
Blues is mixture of European tradition music from the 18th and 19th century filtered through the distinctly African viewpoint of southern blacks. The African influence is clear in the rhythms, but is also visible in the pentatonic sounding music emphasizing the flat III and flat VII. The call and response structure is very European in spite of its use in cotton fields and work gangs. English folk music uses the same call and response structures and the same three chords. The use of a diatonic scale for many of the melody lines also shows a European parentage in Blues. Rather than argue if blues is more African or more European music, the logical conclusion is that Blues Music is uniquely American and represents our common heritage. Blues is what we all have in common and should bring us together rather than separate us.