Examining the pattern: position 1 shifts by +1 (G to H, C to D), position 2 stays the same (O to O), position 3 shifts by +1 (L to M, M to N, R to S), position 4 shifts consonant-to-next-letter. Applying to SONS: S+1=T, O+0=O, N+1=O, S+1=T, giving TOOT.