He probably spoke Indonesian Malay when he was living there. He seems to echo well. That is he can repeat back a word or phrase in another language exactly as he hears it. Such people learn languages easily when they need them and they lose them just as quickly. I do that. When I was 8 years old and lived in Istanbul I could speak Turkish like a native. I remember almost none of it. When I talk to a Turkish person, if he tries, he can drag phrases out of me that I could not remember on my own. I could not truthfully say I speak any Turkish now.
Soetoro’s earlier perfect recitation of the Muezzin’s call is probably a bit of Arabic that he has consciously maintained. I have no doubt that he also learned some Arabic in school in Indonesia. It is integral with study of the Koran.
It's not exactly like "echoing".
What's happened is you've simply retained the ability young children have of learning languages.
Did you know there "others" who can detect what you are doing?