Firstly, I will try to define objectively bad music, as there are actually many ideas about this already.
2. Means to an end: Many cases music has caused hate or unnecessary violence, this is when music is objectively bad. As https://www.newyorker.com/magazine/2016/07/04/when-music-is-violence
argues, we used music to intimidate the opponent, and even used to agitate prisoners. Because of the inherent negative nature of these songs, it follows as such that this music is objectively bad in this case. We want to maximize our happiness gain, utilitarianism claims. But this controversial technique to use music negatively surely violates this moral philosophy and is hence objectively bad. Consider if I made a song specifically to torture terrorists, nails on the chalkboard, screaming at 130 decibels, shredding metal and talking trash about them. This is clearly bad music, especially considering if I played it for anyone else they would be extremely agitated and feel bad about themselves.
Objectively good music is much harder to define, but there are some contenders.
1. Influence on society: Would you admit that, if music caused some good change and educated them, then it has a net benefit? Consider the elements of the periodic table song. (https://www.youtube.com/watch?v=rz4Dd1I_fX0
) It definitively helps children learn about science in a fun and easy way. Some other songs are far more influential, especially tribal songs uniting people together, and classical music revolutionizing the piano. If music can bring people together and improve your knowledge, why wouldn't it be "good music"? As such, you can clearly see some songs can be objectively good.
2. "Objectively good" for the person: It's true that people think differently about music, so overall a song might seem more subjective, especially if its impact on actual humanity is too ambiguous to grasp. But listening to music you love brings you dopamine, the happiness chemical. (https://www.psypost.org/2019/02/listening-to-the-music-you-love-will-make-your-brain-release-more-dopamine-study-finds-53059
) Once again bringing back the utilitarianism argument, so long as you aren't hurting anyone else, the music will improve your quality of life and possibly raise you out of depression, if you are sad. As such, every song that an individual likes is objectively good for them.