One way I have developed to tell the pitch of fiddle tunes (usually in G, A, D, C or the relative minors): I learned that I have a tenor voice; the point at which my chest tone switches to head tones is an F. That, and hearing the tune itself: a high third (B) means it is in G; C fiddle tunes tend to have a ragtime component.
The genetic component may have a linkage to autism:
https://www.kennedykrieger.org/stories/interactive-autism-network-ian/perfect-pitch-autism-rare-gift#:~:text=Perfect%20pitch%20may%20be%20associated,to%20autism.%228%20Dr.
One way I have developed to tell the pitch of fiddle tunes (usually in G, A, D, C or the relative minors): I learned that I have a tenor voice; the point at which my chest tone switches to head tones is an F. That, and hearing the tune itself: a high third (B) means it is in G; C fiddle tunes tend to have a ragtime component.