Is this grammatically correct? What does it mean and can it be rephrased? This is one of the musical tastes I have no one knows about😂

Yes, the sentence is grammatically correct. It means that the speaker has a particular musical taste that is not known to anyone else. The use of the emoji adds a light-hearted tone, suggesting that the speaker finds this fact amusing or perhaps a bit embarrassing. A possible rephrasing could be: "This is one of my musical preferences that nobody knows about! 😂"