I’m experimenting with a Sparkfun mp3 player shield for Arduino, using it to prototype for a sound installation idea. In this prototype there are just simple push buttons, while the final installation is more likely to use sensing or more complex triggers. This prototype allows me to experiment with different sounds and on a small scale, get a sense of how sound transitions might work. For the speaker I’m using my old faithful Fender mini amp, love this little device! I use it routinely for prototyping. The video here demonstrates a setup of simple push button that trigger custom sounds stored on the sd card.
There are tutorials and libraries on the Sparkfun site and Github. I used this tutorial to get started.