Perhaps the most heard electroacoustic technique is tape loops, as old as tape itself. Much of the older music that you might think is electronically made is something like a drip sound on tape, for instance. Other devices used light in some way, such as spinning discs with holes so that when light goes through, there is a circuit.
boof (OP) double-posted this 2 months ago, 16 minutes later[^][v]#1,400,172
"This is the earliest recorded piece of electronic tape music, also known as "musique concrete" or "electroacoustic" tape music." 1944 https://www.youtube.com/watch?v=j_kbNSdRvgo
boof (OP) triple-posted this 2 months ago, 5 minutes later, 22 minutes after the original post[^][v]#1,400,173
This is performance labelled electroacoustic, but really they only meant that some instruments are electric and some aren't, not exactly good, but I had to laugh when the guy started wailing https://www.youtube.com/watch?v=lpnJ1uFNIG8