synthesizer

Short definition from Wiktionary

Noun

1. 1
   An electronic musical instrument that creates its sounds with electronics and generally is played via a keyboard.
2. 2
   An electronic instrument consisting of a module, or a set of modules, that creates its sounds with electronics and does not have any keyboard.
3. 3
   An electronic circuit that generates an electronic signal oscillation with accurate timing from a reference oscillator.
4. 4
   An electronic device that generates electronic signal patterns to test an electronic circuit.
5. 5
   A software program that allows a computer to be used as a musical instrument – virtual instrument