Damn Meedley...that was a nice long explaination...it seems to get a bit complicated with the 7th chords and onwards, but I guess it's just a matter of figuring out what mode has the right notes in it to go with that specific chord.
It gets a lot easier once you start really getting into chord construction and how to read chord symbols. When you're getting started a lot of it is just figuring out, for example, what something like F#7(b9b13) means and how it translates in terms of scale choice. Once you get to that point, it's just a matter of knowing the names.
One question though...I haven't tried this yet, but I just thought of it so I'll ask you anyway...say you want to play a chord progression in the key of C that goes something like I-IV-V. If you use a lydian mode over this, wouldn't the notes clash when you're on the IV chord because of the raised 4th(F#) in the lydian mode. And similarly, if you play the mixolydian mode over this progression, wouldn't the notes clash on the V chord because of the flatted 7 (Bb)? Or is it the case that you would just avoid playing the raised 4th and flatted 7 in each case, respectively?
There are a couple ways about this, and most of it will be dictated by context, what style you are playing, etc. If you were heart-set on using a Lydian sound throughout, you could always play C lydian over the I chord, then change to F lydian for the IV chord, then G lydian for the V chord. It's a little harder to "sell", but it does give you a lydian sound over each chord. That can be done well, but also has a potential to sound very forced/cut-and-pasted if you aren't careful to transition smoothly.
Another option is to just play C major (ionian) over the whole thing. That would sound just fine, but you would want to make sure you're mindful of chord tones and not just playing over each chord as though it were a "C". This is your most feasible and easily executed option. Playing C Ionian over the whole thing produces C Ionian over the I chord, F Lydian over the IV chord, and G Mixolydian over the V chord. The next step in that process would be to THINK in terms of C Ionian for the C, F lyidan for the F, and G mixolydian for the G (which is important because you'll be able to emphasize the chord tones and things will sound a lot more coherent in general). Just make sure you're playing
through the chord changes and not
over them (if that makes any sense). It's nothing too difficult to pull off, but sounds the best in most cases.
The only issue with Warheart's advice to play F lydian over the whole thing is that (just like with playing C Ionian over the whole thing), it will only sound like F lydian over the F chord. Over the C it will still sound like C major and over the G it will still sound like G mixolyidan. In fact, playing F lydian over the whole thing functions EXACTLY the same as playing C Ionian over the whole thing. I would argue, however, that if you get the idea of playing in F lydian over the whole thing in your head you'll have a harder time making it sound good because you'll be thinking in relation to "F" and not "C".
Then there's the approach you mentioned of playing C lydian over the whole thing and just avoiding certain notes that clash over certain chords. The F# over the F chord would be the major one to avoid. As far as playing mixolydian goes, you'd probably be okay. Having the Bb over the G will give a bluesier sound over that chord, which is cool if that's what you're going for, but there's other situations where that's exactly what you don't want. Going back to blues, most twelve bar blues forms have the I, IV, and V chords all as dominant 7ths (which has a major 3rd) and most guys will play the blues scale all over that, which sounds just fine. A perfect example of how using your ears and ignoring what is theoretically correct can yield pleasing results
P.S. I'm very glad that there are people like you on teh internetz
seriously dude, I appreciate all your help.
As always, my pleasure!
