In August 2015, the music critics at Rolling Stone released their list of the 100 greatest song writers of all time. I found the top 25 online, removed the non-Americans for statistical convenience, and then recorded the ethnic background of each one.

Rank (among American song writers)NameEthnicity
1Bob DylanJewish
2Chuck BerryBlack
3Smokey RobinsonBlack
4Mick Jagger & Keith RichardsWhite Gentile
5Carole King & Gerry GoffinJewish
6Paul SimonJewish
7Joni MitchellWhite Gentile
8Stevie WonderBlack
9Brian WilsonWhite Gentile
10Hank WilliamsWhite Gentile
11Bruce SpringsteenWhite Gentile
12Eddie Holland, Lamont Dozier and Brian HollandBlack
13Neil YoungWhite Gentile
14PrinceBlack
15Ellie Greenwich & Jeff BarryJewish
16Jerry Leiber & Mike StollerJewish
17Lou ReedJewish
18Robert JohnsonBlack
19Randy NewmanJewish

Seven of the top 19 are Jewish (37%). But keep in mind that almost all of these people are from the Silent Generation which was likely around 5.8% Jewish (not counting recent older immigrants). Even still, Jewish representation is an astonishing 638% (37/5.8 = 6.38). Six of the top 19 (32%) are Black. Given that blacks were about 11% of America in the 1960s and 1970s (when most of these song writers were most relevant) their representation is an also incredible 291% (2.91). Around the same era, non-Hispanic whites were 87.5% of America, and if we subtract the 5.8% who were likely Jewish, that gives 81.7% of Americans who were likely White Gentiles, but given that only 32% of this list is, that gives a representation of only 39%.

But keep in mind that this list was made by music critics from the legacy media so they have their own biases as we all do. The results need to be replicated by more diverse methods before we can conclude, categorically, that when it comes to writing pop music, Jews > Blacks > White Gentiles.