Definitely a Flash animation.
Watching this video again, I can see you have potential, but you are definitely need to work on some things. I may be incorrect, so don't take my word on a whim; however, I'll list the flaws I saw.
Flat. Some images were quite flat. There was some shading in a few, and I did admire that; it hints at your artistic talent, probably outside of Flash animations. However, it's quite obvious they're flat. Maybe work on thinning contour lines, changing contour lines' colors, and adding more shading. It might increase time, and as you mentioned you were on a schedule, but it was really noticeable.
Lots of tweens. Let me reiterate: lots of filler tweens. At the start with the guitarist, you have a sort of jittery effect with her segment. It reminded me of... hm. Previous music videos? Like, around 1980? Before I was born? Something like that. I enjoyed it, yet it slightly clashed. It reminded me I was watching a flash animation. Not bad... but it got worse.
One part where I totally enjoyed your tweening was when you had a sort of squish: where the singer was doing a sort of fist pump in the air. Totally shocked me: and then you had the guitarist, and she started jumping from frame to frame!... and then it repeated. Like a movie clip. I might be jaded, but a lot of this looked like you set up a few movie clips and repeatedly used them. Obvious.
Also, some of the proportions are off. I mean, I get that you can use foreshortening and chibi effects... but some frames were painfully disproportionate to the actual human figure. Like when you first see the pianist. Just... unnerves me.
Next. Um...You definitely do some effects that I dont' know of. Maybe I could imitate some of the blurs, but some of those lighting effects and how you can slowly fade in a certain color into an entire image... don't know how to do that. ^^;
Ah. And when it's the entire group near the end. I've been learning a lot of parsimony lately, so I might just think there are too many figures in that shot (the one where the singer sorta flies into the background and causes this giant pillar of light to appear (JUDGMENT! ^^; ) ). Or I might be noticing that I've seen each and every one of those drawings/animations throughout the entire animation. If you want a sort of group image, perhaps you could mix it up?
Music was good. You didn't go wrong there.
Overall... good piece. I'm sure that, with some more years of experience, you'll be creating some epic flash animations! :D
Best of luck to you,
~Supersysscvi