How many hundreds of notes do you contemplate creating per frame?
How many thousands of notes do you contemplate having on the screen at one time?
If you have fewer than a hundred, you’re wasting your time with pooling.
As for the objects showing up late, you probably just have a bug. There’s no “buffer” of things waiting to respond to you telling them to turn on.
Time to start debugging! By debugging you can find out exactly what your program is doing so you can fix it.
Use the above techniques to get the information you need in order to reason about what the problem is.
You can also use Debug.Log(...); statements to find out if any of your code is even running. Don’t assume it is.
Once you understand what the problem is, you may begin to reason about a solution to the problem.
Remember with Unity the code is only a tiny fraction of the problem space. Everything asset- and scene- wise must also be set up correctly to match the associated code and its assumptions.
The costs and issues associated with object pooling / pools:
In very rare extremely-high-count object circumstances I have seen small benefits from pooling.
In MOST circumstances, object pooling is a source of complexity, bugs and edge cases while not giving any measurable benefit.