You can transform a toy keyboard into a highly customized MIDI controller, perfect for laying down synthwave pads on your favorite hardware or software synthesizer.
All it takes is an Adafruit Kee Boar KB2040 running CircuitPython, a Meowsic cat piano, and the desire to be awesome. Plus some soldering and a bit of paint.
You can get some spray primer, paint, and clear coat at your local hardware or art supply store if you want to paint the keyboard.
You can use any hardware synth that accepts DIN-5 MIDI (using an adapter cable from TRS-A) or TRS MIDI (may require TRS-A to TRS-B cable or adapter). You can control software synths that can be a USB MIDI host, such as an iOS device or computer.
A great free synth to use on iOS is AudioKit Synth One.