Independant function calls?

[DiamondToaster]

I got busy and started to write an MCSmash plugin (Super Smash Bros. im Minecraft), but I came across a bit of a wall. Lets say I got a sleep function:

function sleep(n)  -- seconds
  local t0 = clock()
  while clock() - t0 <= n do end
end

I want to do a little noteblock music on command, but when I do this:

		function PlayNoteBlock()
			NoteEntity:SetPitch(F5)
			NoteEntity:MakeSound()
			sleep(0.2)
			NoteEntity:MakeSound()
			sleep(0.2)
			NoteEntity:MakeSound()
			sleep(0.2)
			NoteEntity:SetPitch(D5)
			NoteEntity:MakeSound()
			sleep(0.1)
			NoteEntity:SetPitch(F5)
			NoteEntity:MakeSound()
			sleep(0.2)
			NoteEntity:MakeSound()
			sleep(0.2)
			NoteEntity:SetPitch(D5)
			NoteEntity:MakeSound()
			sleep(0.1)
			NoteEntity:SetPitch(F5)
			NoteEntity:MakeSound()
			sleep(0.1)
			NoteEntity:SetPitch(D5)
			NoteEntity:MakeSound()
			sleep(0.1)
			NoteEntity:SetPitch(F5)
			NoteEntity:MakeSound()
			sleep(0.2)
		end

The entire server freezes while that function runs. Coroutines don't seem to help much here either. Any way I could get around this?
Also, the "F5" and stuff are just numerical constants.