Quran says: Alcohol has some positive things but the negative things outweigh the positive things. In a similar fashion. Will they be rewarded for the positive aspects of their sin? Singing is a major sin that has all those negative effects like increasing hypocrisy. But the singer also produces epic amount of pleasure, entertainment and happiness to millions of people through his voice. My question is: Will he be rewarded like the reward of doing a good deed for the fact that he is entertaining and making happy millions of people through his voice? What about the porn actor?
Answer: certainly not.
When some act is sinful then Allah the Almighty in His deep knowledge and wisdom has declared anything related to it as sinful. The best example actually is Zina where even coming close to it is blamed. As for alcohol or riba a whole lot of people who are directly involved with it are blamed and also some people who are indirectly involved in the consummation.
Singing is considered a sin by many if not most scholars. Listening to a singer is also a sin for those scholars.
The same is the case for porn as Zina is haram and even watching or looking at the 'awrah of a non-mehram person (not necessarily the intimate parts) is haram (Zina of the eyes).
So in both cases we are talking about a bad deed which is haram and would be registered as such for all the performer, the listener or the person who watches it.