Piano helped visualize how to read to begin with
Then trumpet made me learn to transpose
Bass was kinda easy after I learned the previous ones, but taught me how to use a basic fret board (one note at a time)
FWIW I can work with other musicians much better because of learning theory how I did
So I consider that my most useful music tool
Good advice.
Piano and music theory seem to be somewhat of a common theme.
The piano/keyboard gives you a linear and visual representation of available notes and music theory gives you a language to communicate with others and helps with understanding of how music actually works.