I mentioned My Singing Monsters earlier; I've been playing that a lot recently. I discovered it through an ad in Crossy Road (which I discovered via ATP. Also, when they compared notes on high scores, I was about 100 ahead of Siracusa, and have added another 80 or so since), and eventually tried it out.
The idea is that you can breed different monsters, all of which have different songs. You can make buildings with the money they generate, which can help you to make more, and bigger, monsters.
It's all very cleverly set up, with five different elements and five islands. Each of the islands supports four of the elements, and you can breed within those four elements. Each monster has one to four of those elements in its make-up, and each breed sings a different part in that island's song.
And as you'd expect, you make bigger monsters by breeding together ones with some of the elements.
Each island also allows several weird combinations that can breed an ethereal monster, which has different characteristics, and can go to the ethereal island. There, they can breed even more ethereal creatures.
The idea and execution really nice; excellent graphics and sound. The game play is actually very much like Tiny Tower (which I haven't played in months; maybe even a year). Having played TT previously helped, as I realized early on to conserve diamonds (the more valuable of the two currencies in the game. You can easily waste them hurrying things up; don't!
Anyway, it's a fun game; I'd recommend giving it a try if you like resource-management games.