Why isn't the sound that I'm trying to make rise in pitch rising?

local a=1
while a<10 do
	game.SoundService.allstar.PlaybackSpeed=a
	a=game.SoundService.allstar.PlaybackSpeed+1
	wait(1)
end

This is a script i'm using (allstar is the name of the sound i'm playing) and I need help making a loop like this so that the song speeds up until it's incomprehensible.

OH I THINK I UNDERSTAND NOW, so the a=blablabla =+ 1 can be a problem. NOt that its not in quotes. quotes are for string). but i think its that when you set variable that equals something then does something to it, its kind of like a function, so its mor like a = do this, and that is not a number so i cant be less than 10, so do this maybe?:

local a=1
while a<10 do
    game.SoundService.allstar.PlaybackSpeed=a
    a=game.SoundService.allstar.PlaybackSpeed+1
    wait(1)
end

to

for a = 1,10,1-- makes sound volume go from 1 to 10 by ones.
    game.SoundService.allstar.PlaybackSpeed = a -- preforms action on this sound
    wait(1)--wait 1 second, 1!
end

So basicly i litteraly changed like the whole thing to a for loop until it finishes. This makes every second the sound or whatever goes 1 higher because a means go from 1 to ten by ones so every second yeah, it does that. Hope this helps / answered this :D

OH and by the way in case you dont know, dont waste storage in workspace, make a script in ServerScriptService and put this code inside and script will work. kk dude;)

local SoundService = game:GetService("SoundService") -- Sound Service
local Sound = SoundService:WaitForChild("allstar") -- The Sound Object

local Pitch = 1 -- PlaybackSpeed
Sound:Play()
while Pitch<10 do
Sound.PlaybackSpeed = Pitch -- Changes PlaybackSpeed
Pitch = Pitch + 1 -- adds 1 to pitch
wait(1) -- waits
end