An electronic musical instrument, usually with a keyboard, that makes sound electronically. Because the sound is built up from scratch rather than coming from a physical string or reed, one synthesizer can produce many different sounds — an imitation of a violin, an organ, a drum, or a sound that no real instrument has ever made. That last part is what musicians find exciting; the imitations were only ever half the point. It appeared in popular music in the late 1960s and 1970s and shaped the sound of the 1980s completely, and today most electronic and pop music you hear started life on one, often as software on a computer rather than a physical box. The word is fully standard and neutral, though in everyday speech people usually shorten it to 'synth'. You will also meet the word outside music, in a more literal way: a 'speech synthesizer' is the machine or software that turns text into a spoken voice — the technology Stephen Hawking used, and the same idea behind the voices in your phone. Anything that puts pieces together to make a whole can be called a synthesizer, but music and speech are where you will actually meet the word. Note the spelling: British writing often uses -iser, American -izer, and both are correct.