I was listening to the radio at some store the other day and Toby Kieth's "Gonna Get My Drink On" was playing. It occurred to me that the melody is nearly identical to Tim McGraw's "Indian Outlaw." Also I always thought Hank Williams Jr. ripped off Cat Stevens (or was it Harry Chapin?) with "A Country Boy Can Survive" because it sounds a lot like "Cats in The Cradle." There are differences but the songs are too similar to be coincidental. I was once writing a song and I thought I was on to something till I realized it sounded just like "Shooting Star" by Bad Co. I guess a tune can get in Your head. You just need to do Your homework to make sure it's your idea.