You have to cut the song at the point where the seasons would change and place the second part over the other Obstacle Course song. That way, when the seasons change, the song will just keep going. Alternatively, you could just place custom songs over all of the other songs and set Obstacle Course to zero chance.
Hope that helps.
How do you know when the season changes? Do you have to mark it down? Like lets say it changed at...2:04, so if your custom song is 4:27, you would cut it at 2:04 and then put another song there or something...?