put a lyd on it (flat-7, that is...)

The Lydian flat-7 (aka the "Overtone" scale) is the 4th mode of the melodic minor scale. One mood that it is able to evoke (for me, at least) is one of "mechanization". Here are 3 examples, and they're all cartoon related.

The first one is called "Powerhouse" by Raymond Scott. No, it wasn't written for the cartoons, but it got used by Warner Bros. in some Bugs Bunny things, and that's where I heard it as a kid and forever have those 2 things linked in my brain. This is just the first theme (clicking on the images will enlarge them a bit):



The second one is the theme song from the Jetsons.



(The first lick above is instrumental and the theme proper -- "Meet George Jet-son" -- starts on the downbeat of the 2nd measure.)

And the third is from the Simpsons.


Of course there's more going on here than just a certain mode: the rhythm of the melody and the underlying accompaniment have a lot do with projecting that mechanized, futuristic feel. On the other hand, all things being equal (like the rhythm), this does seem to be a good mode to use for those occasions.

By the way, in improvisation one can see a rationale for the Lydian b7 (even if it weren't a mode that existed all on its own, anyway) by looking at the regular old Lydian. That is, the Lydian is used somewhat in place of the Ionian to get a raised 4th; similarly in the Mixolydian one might also desire a raised 4th...et voila! the Lydian flat-7.

Oh, yes, you can easily find all of the above tunes on youtube, etc, if they aren't a permanent part of your memory yet.