Thanks for your quick reply @scudly!
I think the Minim library I mentioned allows for that. It offers both an audio player and FFT class with public APIs that look more usable. The audio player class for example, has a method to move the playhead around. So I guess using that I can set it at the right position for every frame and fetch the FFT values.
Regarding the x += 1 example. I didn’t mean I’m keeping track of the frame count myself by incrementing a custom variable. I just meant that I’m used to update values (e.g. coordinates or color values) every iteration of the draw loop. However, I mentioned it because I was a bit confused. Those updates will work regardless, because the amount of iterations won’t change. Hope that makes sense.
Now I have to dive into getting the right buffer size, sample rate, etc. so I end up with 30 values for each second. Not too familiar with this, so that might take a while.
If I have something working I will post it here for anyone interested. Open source for ever!