When music chose G.O it was most likely with the understanding that he would not be limited to only singing. It was going to be full immersion which included writing, composing and arranging. Thankfully, there are many avenues an artist of his caliber can take when music becomes his life force. The OST is indeed one of those avenues. And ok. it may have been helpful that G.O’s bandmate was cast in Iris II, but I believe 바보같 은나 [What A Fool I Am] would have landed on its OST (or any other, for that matter) because not only is it perfect OST material, it is simply a well-written song.