A simple Arduino based synthesizer (using Auduino), and a CMOS-logic chip based sequencer, marking both the first dive into mixing music and sound with the interest for electronics, as well as a professionalization of electronics projects, with custom enclosures and PCBs.
While working on the Auduino synth, I got into other kinds of small synths and build an Atari Punk Console into a telephone, and made a matrix mixer to connect all of that together