Samply - DJ Sampler lets you compose music easily using your iOS device. You can load different samples from your iTunes library to any button. You have 16 buttons and 3 sets to play with which leaves you with 48 different samples. To load sample hold the button few seconds and iTunes library will appear. When you choose the sample you can play it by tapping the button or you can edit its settings by opening sample settings and do a bunch of other stuff. You can save each set with save option and load it anytime.