I got biab because I want to be able to easily and quickly get a backing track together. At its simplest this works very well. I.e. put in the chords and select the backing you want and bingo you have it.

For that you only need a PC, which will play the biab track fine through its own soundcard.

To add vocal or your own guitar and such you need a digital interface like the focusrite. This also plays back through the PC.

A modern keyboard with USB connector, plugged into the pc, will get picked up by the interface and playback via the soundcard. Usually that will give you a default piano sound.

But anymore than that basic setup and you will need to learn all about the various settings and configurations to achieve what you want with different pieces of equipment.

Using: Dell 3268 i3, 8 GB ram, windows 10. Biab version 2017 standard package, no extras.