Love the way you thought about the theme. Name hooked me and when I read zombies I was in (we have apocalypse in our game too!).  I waited for quite a bit for the 2nd wave but thought it crashed and then saw a few comments about that needing to be sped up or adding a button to call more, which I agree. I almost would work that into the 'rewinding' of the speakers, purhaps add a bar to show the player that more zombies have been called... I can see myself playing waves of this if so :) 
Great choice of music and spooky shadows gave me the right feel. Also assets of speakers having wind up I liked.  One point to keep you 'in world' is that I would try to fade the music in and out so you can't tell when it stops and starts. All in all great effort for a one person game!

It took really long after the first wave to spawn the 2nd wave, I actually thought the game might have crashed. Same for the 2nd and 3rd wave; I quit after that. The 'rewind' labels are in front of the one below them; it might have been clearer to just change the sprite color of the wind icon to indicate it needs to happen, and maybe add a button to call in the next wave; that way, players can choose their own pace and won't have to wait on an empty screen.

The idea  was great and simple to the player understand since the beggining. The only point is the bug that other players commented too. 

Great job! I hope see more of your work. See ya~

Though the game-play itself might be basic. I have to give applause to an interesting take/spin on the Rewind theme.

Is there only 1 wave? no more zombies spawned after i killed maybe 4.

I like having to manually reload in games, it naturally adds a sense of tension in games. I ended up getting stuck on wave 1 a couple times due to a bug

The game seems pretty cool but for some reason i can't past wave 1, zombies just stop spawning.

cool concept, sometimes the zombies would attack the wall at a weird angle and I can't do anything to stop them, I suggest have 4 - 5 points the zombies attack instead of the whole wall. Other than that it's cool. 

I had fun with this!  I think this game has a lot of potential if you were to add different maps and locations.  Also, more animations and effects would make the game feel more alive (zombie death, wall breaking, etc).  Great work!