A music synthesizer. It's a pathway to learning electronics, music, and the nature of sound. There are cheap kits, cheap synths, lots of kinds of synths, and there are much more complicated and expensive systems you can grow into. You can get software synths also, VCV Rack is a free though complex one:

https://vcvrack.com/

However I'd recommend an inexpensive hardware one with real knobs you can turn, like one of the Korg Volca series:

https://www.korg-volca.com/en/

Recording the sounds can lead into exploring all the concepts and gear involved in recording and mixing music. It's not mutually exclusive with doing other things also, you can play with both synths and computers and being involved with something artistic can add dimensions to and an escape from the nature of classwork/work.

Some other suggestions: gardening, high voltage electronics (with lots of supervision), electronics, photography, movie making, ham radio (gnu radio), show lighting systems (there's more than disco lights, robotics is involved), robotics, acoustic instruments (guitar, piano, flute, drums), sensors (you don't necessarily have to know electronics, get a data logger with built in sensors), weather monitoring/forecasting, hydraulic systems (with supervision), wood working, metal working, 3D printing, bird watching, painting, minibikes/small engines.