In almost every sadhana, yidams or sacred objects arise from a seed syllable. You have referred to them as being like speed dial to whatever we are bringing up. Other than that, I have never heard a Dharma teacher talk more about them. Where does this come from? Why not just visualize the yidam, etc?
I think it might be like the subtle vibrations, an intention first arising to manifest into something seemingly more complex or evolved. Anyway, I'd like to hear if there is more depth to this subject. Thanks.