Music Demo being threaten to be sued..

[Nickatnite]

What is the name of your state (only U.S. law): Michigan.

Hello,

I was hired under a guy who wanted to learn more about music and produce some of his music and so I did and we didn't sign no agreement or anything. So anyways he said he'll opened his house to me if I wanted to work on my own music and stuff, so he let me use his equitment for me and my friend to use. So then all of a sudden one day after helping him on his stuff, he asked if everything that we work on does he get "Part-Ownership" of the song? I told him yes in which I thought was about his songs so anyways the next day he gives me an "Ownership agreement", in which said that one of my songs would be be part ownership towards him as well, I flipped out and said "No way" and shoots me back with a "Well you agreed, its an oral agreement", in which I NEVER AGREED ON!! So I told him he was crazy and left. So he is threaten to sue me I ever use that song without his permission. He also said he will be sending me something stating his beliefs on the song and that he feels apart of.

So should I be worried? I mean he isn't even in the damn song, I wrote the lyrics, produced it (at his house on my own time), My friend played guitar (were in a band) and I did the vocals, he never did anything!! WE DIDNT EVEN SIGN ANYTHING! and yet he uses an oral agreement on me, We did think about him doing Organ for it however we decided not to at the last minute.