Mars Neptune in musicians' charts?

1
When I have looked at a lot of famous rock musicians' charts, the pattern that seems to come up typically is Mars Neptune, with connecting planets in between and sometimes the Moons Nodes, but the core of it is Mars Neptune. Occasionally Mars gets replaced by Venus (eg Leonard Cohen and Colin Vearncombe, the latter had transiting Neptune opposition his natal Venus when he wrote his famous song "Wonderful Life"). And occasionally Neptune gets replaced by Pluto, e.g. Ian Curtis of Joy Division, with his Mars Uranus Saturn Pluto.

What this made me wonder is, rock music has only really been around since about the 1950's and 1960's. People with these kinds of aspects in their charts, how did these manifest in previous centuries when musical genius was not especially valued and minstrels were not rich? Out of curiosity I looked at Leonardo da Vinci's chart, and noticed that he has a 45 degree semi square between Mars and Neptune.
http://www.astro.com/astro-databank/Da_Vinci,_Leonardo
Also Pluto is conjunct his Venus' antiscion and square his Sun.

So just maybe Neptune and Pluto represent genius, which has manifested in this tiny bit of history since the second world war for those whose Mars or sometimes Venus aspect them as socially valued and rich rock musicians?

2
i have a friend - 95 years old.. he doesn't have a musical bone in him! well, i suppose if one had put him in a different set of circumstances, it could have been different.. aug 21 1921... no time of birth for him.. mars conjunct neptune in leo either way..

i think these kinds of generalizations break down and fall apart really quickly.. it is like saying those with mars/neptune might have alcohol problems or be homosexual and etc.. i think all one can say is mars connects to an outer planet and we don't know what it means or how it will unfold in the persons life.. so, i guess i am not in favour of your theory!

3
Leonardo da Vinci wasn't known for being a musician, was he?

Maybe your friend is a genius in another way than music?

I seem to remember that the chart of the artist Richard Dadd has a very striking Venus Neptune (and I think Chiron), in a T square. He wasn't known for music, but was one of the most talented visionary artists ever.

4
Mars is not really typically a musical planet - but it has been known for a strong voice.

Neptune is indeed an artistic and creative planet and so is Venus.
Neptune to Venus or those two connected with angles or the luminaries and you most probably have an artistic person.