"There was a musical change."
Translation:Hubo un cambio musical.
In short, "hubo" is simple past tense - indicating an act that happened, for a discrete amount of time, and is over. "Habia" is imperfect - indicating an action that happened in the past over an unspecified period of time and might still be taking place; we're not sure if it's ended or not. Or it might be a general condition (e.g., there was a table in the room). Imperfect is also used when telling stories (things that, obviously, took place in the past).
See this thread for more - https://forum.duolingo.com/comment/12007/Hubo-vs-Hab%C3%ADa
The only problem with the imperfect is that the imperfect normally implies it happened over a period of time where as this was a change at a certain time it seems. The way I learned and remember is hubo un terremoto (earthquake) only once. And había incendios (fires) because they continue. Sorry for the long winded answer