I'm not sure when the following were invented but they came into their own during the 80's.
Alternate synth trigguring devices such as guitar sythns and drum pads.
DX synth based sounds. (First decent non-analog synths)
Work Stations.
Cassette multi-trackers.
Digital Effects (especially for guitarists and also especially in a "rack mount" design.)
Midi, Sequencers, Samplers and Drum Machines. Yes they were around in the 70's but they didn't get much attention till the 80's.
Digital Recording
The tape size and speeds of multi-track reel to reel machines got smaller for the budget studios.
The Fostex A8 comes to mind.
Smpte time code (I think.)
The ability to store midi modulated frequencies onto cassette tape. I know this was invented much earlier but no one used it much in the music field for midi to any large degree until the 80's when we suddenly got this proliferation of drum machines and sequencers on the market.
Dolby C and later A.
Electronic transports for cassette units.
Direct Drive motors came into vogue on both cassette decks and turn tables.
Also better tape formulations for cassettes and reel to reel started taking off.
PZM mics
Integrated multi-layered circuit boards made their way from the computer market to music products such as mixing boards, thus making them a lot cheaper (like the first Alesis Board) but also much more costly to repair because you often had to throw away the circuit board and get a new one over small problems. If you simply blew a pot that was integrated into the board there was no way to fix the individual componate.
Fender came out with their first solid state guitar amps and started a trend in guitar amps that also trickled down into PA Power Amps such as the Peavey Decca series.
Hmm...that's all I can think of off the top of my head. I'm sure that tomorrow a few dozen other things will pop into it that I'll wish I'd have said.
