I want to spice up my solos over a Blues progression. I already can play a variety of scales but the Diminished scale is something I would like to add because of the particular sounds it creates. In what ways would I use it to enhance the solo? Thanks.
In a standard 12-bar I-IV-V blues progression (here in F)
||: F7 | F7 | F7 | F7 |
| Bb7 | Bb7 | F7 | F7 |
| C7 | Bb7 | F7 | C7 :||
there are three places where you should start trying to incorporate the diminished scale:
bar 4, where the F7 chord can be interpreted as a dominant chord resolving to Bb7. Here you can add tension by using the half-whole scale (F-Gb-Ab-A-B-C-D-Eb) which adds some altered tensions to the F7 chord that resolve nicely to the Bb7 chord.
The second place is bar 6 where Bb7 moves to F7. Here we cannot simply interpret Bb7 as a dominant chord resolving to its I-chord, because in this case it should be followed by a chord with root Eb (Bb is the V of Eb). However, in your solo you can substitute the Bb7 chord in bar 6 by a B diminished seventh chord (Bdim7). This basically just means to move the root up by one half step and leave all other chord tones unchanged. You do this substitution by simply playing the B diminished scale (whole-half) over the Bb7 chord in bar 6. In this way you create tension which resolves to the F7 chord in bar 7 (Bdim7 resolves to F7/C). This substitution (Bdim7 for Bb7 in bar 6) is commonly done in a jazz-blues. But even if the chord is played as a Bb7, you can do this substitution in your solo.
The last place is bar 12 where the C7 chord is the dominant chord resolving to F7 in bar 1. Here you just do the same as in bar 4 (but with root C instead of F): you add tension by playing the C half-whole scale over C7 which resolves to F7.
The 3 bars mentioned above are the most obvious choices for using the diminished scale in a I-IV-V blues. Of course you can play the diminished (half-whole) over every dominant-seventh chord, but if you do this in a simple blues progression, you will stop sounding bluesy.
If you're interested in using different scales over a blues progression, you should check out this example by Oz Noy: Scales over 12-bar Blues
Consider the half whole diminished scale: R b9 b3 3 #4 5 6 b7 R
All notes except one are very commonly used in blues soloing.
the inclusion of both the b3 and 3 gives the essence of blues (mixing major and minor). The 'blues note' (b5/#4) is there. All of the chord tones are there. The 6 is there. So it suits blues very well.
Try these over a dominant chord: (notes for an A7)
b3 3 R (C C# A)
.#4 5 b7 R (D# E G A)
6 b7 R (F# G A)
They are all very familiar sounding blues licks.
However the b9 is very rare in traditional blues. The fact the scale has only one 'outside' note (in a blues context) makes this scale a great introduction to more outside jazz & fusion style blues. As for your question, to incorporate it into your own playing you use that same method as you would (or should..) for any other scale: learn licks! Listen to jazz and fusion and you'll hear this scale often.
Here a short one to get you started (in A)
A C C# E G Bb C C# A
All ascending except for the final C# to A.
I won't mention the whole half dim. scale as it is nowhere near as useful in a blues context for reasons that should be obvious:
R 2 b3 4 b5 b6 6 7 R
There are two diminished scales, the half/whole and the whole/half. This translates ,in C,as C,Db, Eb, E, F#,G, A, Bb, for the first, as it jumps semitone/tone, etc. The other works starting with C, D, Eb etc.Both work best over a diminished chord. I have used note names as they came, not particularly accurately.
To fit into a solo, one way is to look at a bar, say, C7, and check which notes will fall on , say, beats 1 and 3. A run of triplets using the first 6 of the half/whole would put a C on beat one, E on beat two. If that was repeated, it would mesh in with the C chord underlying.
You may find that the other sounds better - or continue the rest of the bar going up. Key notes fit in key places, sometimes with a bit of re-timing, but that's what it's about .Try it. If it sounds good, it probably is.And vice versa...
If you're thinking just of the notes a tone and a half apart, they fit best over a diminished chord, more like an arpeggio.
What Fergus said is true if you start a diminished arpegio from any chord tone but the root. Lets say you are playing over A7 (A C# E G) If you start a diminished chord over the 3th, C# you get C# E G A# over the 5th, E you get E G A# C# over the 7th, G you get G A# C# E
All the above had the same chord tones as a rootless A7 b9
But if you start a diminished chord from the root of A, you will not get those notes.