A few of the songs in Phantasy Star Online Ep 1 & 2, as well as Phantasy Star Online 2 are very neat. They're a bunch of small clips of music (6 seconds for PSO ep 1&2, unsure for PSO2), that somewhat randomly sequence together depending on what's happening. This is why the official soundtrack for ep1&2 has a lot of missing tracks, and PSO2's has a lot of excessively long tracks. for ep1&2, I'm guessing they didn't feel like simulating it, while for PSO2, they decided to simulate them for extended periods of time.