The samples are thought of as oscillators, and effects and modulation are added by dragging them into a page and connected with wires. It's easy to do and the graphic interface makes it quite intuitive Certainly easier than a lot of hardware samplers. Most of the time, Unity will gets its MIDI input from a keyboard or a sequencer, but Unity has a keyboard app built in. Programs can be selected from the keyboard app. There is also a mixer app to route the outputs of the banks and add global effects if they are necessary.
Sound quality is a mixed bag.
As a sample playback system, Unity is fantastic. However, the internal resolution offers the possibility of very high quality effects, but the sound doesn't deliver on that potential. My advice is to bounce down to audio tracks and use your normal effects boxes or programs. The filters and such are supposedly derived from the Retro AS-1 engine, and sound about the same. They aren't my favorite software filters, but they certainly don't suck.