Intercostals are the muscles that can elevate ribs when they go into spasm. Mine can do so very suddenly in which case I get a sharp pain, or they can sneak up on me, the bastards.

And IIRC, my current PT (Ando in Anaheim) called out rib 3 as the one that when elevated can stretch and stress the pec minor. A web search for "rib 3 pec minor" (https://www.google.com/search?q=rib+3+pec+minor) is showing me ribs 3 - 5 as the connection.

When I learned how to show my ribs back in, I started having far fewer pec minor pinch sensations. This was a recent development.

HTH