At highway speeds, the wind is loud. The engine is often loud even with a factory exhaust. The only audible signal that's likely to matter is a car horn, and th

At highway speeds, the wind is loud. The engine is often loud even with a factory exhaust. The only audible signal that's likely to matter is a car horn, and those are loud enough to hear over music at reasonable volume. Cars are quieter, and hearing other vehicles is more likely. If anyone shouldn't listen to music, it's car drivers, not motorcyclists.