I, do not like to disagree with you on your site, and I would be more careful if it was something you actually wrote... I don't remember disagreeing with anything you actually wrote.
But I do not agree with this research such as it is, there may be more data or perspective that proves this right but, Sag asc. Libra MC, Venus 13 Gemini is not enough to show one of, who is thought by many to be THE greatest lyricist of all time. Bob Dylan. His music, and being, is clearly Neptunian, 'Twilight over frozen lake, a North winds about to break'. I would have more of a tendency to believe this if Neptune had been featured. Most people will have something at those degrees.
I do not know much about the area of musicians and astrology but someone can basically look at a chart and see how the musician operates so since that is all I have to go on, that's where I will start. I would focus on what I can see in a chart.