Ok, here's how to beat The End(final boss). You want to keep their minions as far back as possible before he comes in. When you're ready to bring him on, send in 1 or 2 angels to take out the enemy castle along with a ton of everyone else. After you've destroyed his castle, keep spamming everything including the Angels. The small units slow him down but are close to damage to him. Don't forget to spam all your arrows as well. If you have everything at the max upgrades, even spamming everything you should still have your mana keep going up. With the dragons and angels, you want to alternate when sending them out.
I got a(n) A+ on medium! My score was 1917714 with a max combo of 213. I scored 150 perfects, 63 greats, and 0 goods. I got only 0 bads and 0 misses! I was playing on 9 speed and had 0 crazy options on. Great game, I like it! Play it here: http://www.thorgaming.com/games/3926/feel-the-beat.html
 "The Last Stand 2"){kind=icon}
 "Mud and Blood 2"){kind=icon}
 "Amorphous+"){kind=icon}
 "Shadez: The Black Operations"){kind=icon}
 "Epic war"){kind=icon}
 "Feel the Beat (F2Jam)"){kind=icon}
 "FWG Bridge 2"){kind=icon}
 "Age of War"){kind=icon}
 "Ragdoll Cannon 1.5"){kind=icon}
 "Kongai"){kind=icon}
 "Music Catch"){kind=icon}
 "Modern Tactics 3"){kind=icon}