First time mom here with a 21m old who keeps singing ABC/ 123 / rhyme (gibberish mostly but right tunes) which he has learnt so far even without being asked to . Like he says this whenever he wants to . Is this normal ? Is this how they learn it ?

Also says bye to even non living things apart from waving to people . Like when he sees a train passing , he points “mommy train” & says “bye bye” is this also something toddlers do?