The project stemmed from a need to retain these controls whilst hosting a tenkeyless keyboard in my current setup.
The macropad uses a minaturised Leonardo board from Jaycar electronics. However any board with USB HID functionality such as a Pro Micro would be also suitable for this project. Making up the core of this project is the consumer API from NicoHood's HID-Project. Through the use of the multimedia functions within this API, the macropad is OS agnostic and is plug and play for your multimedia control needs.
Micro looks like a more expensive dfrobot beetle https://www.dfrobot.com/product-1075.html
I used one to make a similar small 3-input macro controller with a couple LED indicators