Dude was always vocal and clear about what he did on their beats. Even Kelis used to speak about who did what on their production. Chad is an actual instrumentalist. So all that lush sh*t we hear on those classic Neptunes beats, and the dope chords on sh*t like "Frontin'", "Excuse Me Miss", "Get Along With You", "U Don’t Have To Call", "Beautiful", etc. That's Chad.
He's too overlooked, but with a GOAT discography. And that's because Pharrell likes being in the front. But Chad was the one that really made that Neptunes sound hit the way it did, musically.