The ondes martenot and trautonium were continuously developed for several decades, finally developing qualities similar to later synthesizers.
In the 1980s, the invention of the relatively inexpensive Yamaha DX7 synth made digital synthesizers widely available.
1980s pop and dance music often made heavy use of synthesizers.
They are often played with a musical keyboard, but they can be controlled via a variety of other devices, including music sequencers, instrument controllers, fingerboards, guitar synthesizers, wind controllers, and electronic drums.
Synthesizers without built-in controllers are often called sound modules, and are controlled via USB, MIDI or CV/gate using a controller device, often a MIDI keyboard or other controller.