Answer:
a positive externality if you like the music, and a negative externality if you don't.
Step-by-step explanation:
Positive externality: The term "positive externality" is described as the benefits that are being enjoyed by individuals outside the marketplace because of a specific firm's actions yet for which they don't pay any particular amount.
Negative externality: The term "negative externality" is described as the "negative consequences" that are being faced by outsiders because of a particular firm's actions to which nothing is charged by a market.
In the question above, loud music could be a positive externality if someone likes the music whereas negative externality if someone doesn't like it.