Sam Allardyce's side have now won four of their last five games, and Song, who was named man of the match in the win over City, cites a togetherness within the squad as the primary factor in their recent wins.
"The key to the win on Saturday was team spirit. We attack together, we defend together and at the moment we are playing great football," he told Sky Sports News.
"All the boys together are happy. We enjoy training together and that is why it is easier to play when you come to the pitch.
"Now we have to continue to improve game by game."
West Ham face Stoke City at the Britannia Stadium on Saturday.