Your code is a bit confusing (you could make intermediary variables, eg. to store timbreSegments.get(i).get(j) which you call repeatedly) but on a quick look, it seems OK for your purpose. You explain well your need, you managed to code, but you don't explain if it is working or not, and if you have a problem with this code. We cannot run it to check it...
Now, it seems you over-engineered it...

If you look again at what you coded, you don't really need String keys, the prepending of "t" to the number is a bit artificial (but logical given that you thought about dynamically generated variables...). So, you can have a HashMap<Integer, Float>
But this one is useful only if the integers are not consecutive. That's not the case here.
So, after all, you can just use good old arrays to hold your data!