A.L.
There is nothing wrong with your son! Motor skills and cognitive skills have their own developmental timetables. It is not important how your child is measuring up to others his age, what is important is that he is progresing at his own steady rate. Where language is concerned infants develop receptive language first, which is why he seems to acknowledge your talking and singing. A first word can be expected between 12 to 18 months. First words are typically names of primary caregiver and/or favorite items. This level of development is quickly followed by two word sentences like "doggie gone" "car go", etc. You are doing the right things.Continue to sing and read to him and be sure to verbally label his environment to help build his vocabulary. By the way, I am a mother of 3, and an Early Childhood Professional, currently taking college courses on this very subject! ;)