I have been playing My Singing Monsters since last Fall, and have really enjoyed this app game. You choose monsters to place on your islands, and depending on which ones you choose and how many of each, you will have a different sound. Each island is a little different, and the sound of each type of monster changes on each island. You can choose to put real money into the game, but it is in no way necessary- I certainly haven’t.
I think the main drawback to a game like this is that it takes patience to build your islands up to a point where they sound really interesting- it does not go quickly, and you can’t speed play up beyond a certain point. You can only collect ‘in-game money’ from your monsters at set intervals, so there are long periods of downtime in between where it’s best to go away from the app and then come back later to continue play. It can get mind-numbing if you aren’t careful.
There is a really cool video about the making of the app on YouTube:
YouTube Video, Behind the Scenes: https://www.youtube.com/watch?v=95Au-7V9PSY
My Singing Monsters official webpage: http://www.mysingingmonsters.com/home/