It could be coming at any time in the next hundred and forty years. Better prepare now!
Similarly to the gravitational waves that shaped the Milky Way, another kind of wave spins around the galaxy, at a much faster pace. It is a resonance wave, carrying an inordinate amount of resonance that enhances any Song in its wake. While the speed of the galaxy's spiral arms is barely noticeable at an individual scale, the resonance wave, also simply called the Wave, travels at a speed of several light years per second. Stuck in a spinning motion, it crosses the same place every thousand years or so, a tantalizing spectacle to behold.
The Wave has a length of a billion kilometers, which is rather short compared to its velocity. Nonetheless, it has a lasting effect on the places it crosses, enhancing any Song. This effect lasts for several days after the passage of the Wave, boosting everything. This period is always extremely hyped, and life becomes tumultuous for a moment before everything dies down. Ordinary peoples discover the realm of masters, and masters enter new musical dimensions altogether. Things can get a bit dangerous too, but a few injuries and casualties are not enough to drown the global euphory of the event.
Excited by the perspective of an elongated time in the wake of the Wave, some people ready up the fastest ships and gather a crew of skilled musicians in the Song of Acceleration. With their enhanced music, they are able to reach phenomenal speeds, dangerously breaking the laws of physics to savor just a little more the euphory of an unleashed Song. They never reach a fraction of the speed needed to follow the Wave, but do enjoy it longer than others. Each time, a race is organized, with a great number of victims. At such speed, a slight mistake in navigation or a tiny speck of dust in the way is fatal to the whole vessel. The best racers of each competition are lost without exception, with the surmise that they reached such a high speed that they dissolved in space, lost body and soul.
Another kind of rider believes they can use the Wave to venture into the Silence Zone without losing their minds. The part of the galaxy outside of the Obelisks of the Song of Things' network is filled with a dangerous Silence. For some reason, the Wave is not affected by the abnormal emptiness and may be the key to life in this forbidden part of the galaxy. And so each time they set sail, hoping to cross the area fast enough before falling behind the Wave. None ever returned.