Audio processing is interesting to students. For just $87, we have a nice audio mixer. We have five microphones, including a sophisticated, directional "shotgun" mic. The mixer has built-in reverb controls.
The mixer has a record/playback capability that can connect by Bluetooth to a smart phone, and by USB to a PC or USB Flash memory. As of August, Mr. John has had a little success with this, but there is a lot more to be discovered.