Two that readily spring to mind are Django Reinhardt and Stefan Grapelli. Having them both playing together must have been quite something to witness.
That they are still vaunted as the best of their genre 70 years later is testimony of their skill and inventiveness.
The term genius is easier to apply to big thinkers like Einstien or Newton. Music is too subjective and open to interpretation.
Some might say that Hendrix was a genius because he was the first of his type, others might prefer Elton John who has an amazing gift of being able to churn out a hit song in minutes.
There are many great musical innovators but by it's nature all music has its roots in someone elses' work, making it all the more difficult to quantify.
I can say with certainty that I do not fall into the category!

C-flat.