The way to do this without lag is to load the entire file into memory. MMP3File is not loading the entire file into memory, it reads it as it needs it. I imagine you are running out of memory because the way it reads it is by decoding many successive small chunks and the discarding the array. However, if you are skipping a large amount, I imagine it would be possible for heap space to be eaten up before the garbage collector kicks in on the discarded arrays.