No, not gonna go into a tune during a chat and really its that change in pace and feeling like your saying something in such a different way that it feels like substitution, it doesn't have to be singing.  Sometimes you can just change your pace and feel like your saying something totally differently from the way it was qued up in a stutter state.  I always wondered if thats why sips used to say to talk slower, had that same change/substitute effect.