A type of delay or echo processor that uses analog recording tape to achieve the effect. Back in the “old days”, producers and engineers created delay and echo effects using tape machines. Basically a signal would be routed to a separate tape recorder (from the one being used for the performance) that was set to monitor off of the repro head. The slight delay that occurred between when the signal was presented and when it finally came off the repro head provided a delayed signal back to the main recording. The delay time could be adjusted by changing the speed of the tape machine used for the delay. Feedback or multiple echoes could be generated by routing the delayed signal back into the machine, and other, more exotic effects could be created by changing the speed of the machine while signals were passing through it. When applied subtly chorus would result, but other more dramatic effects were easy as well.
This technique became so popular that engineers began to devise ways to make the tape continuously loop on a machine so the tape would never “run “out”. Manufacturers eventually stepped in with products to make it easier. The Echoplex and Roland’s Space Echo Series were some of the more popular devices. They had features and controls that were optimized for the intended purpose and used proprietary tapes that were already looped and in small cartridges. These machines were tremendously popular because they were easy to use and portable. Besides being great delay/echo units they were also many musician’s first foray into looping effects.
There were some significant downsides though. It was tape. The recording quality wasn’t always great, depending upon the condition of the heads and how worn the tape was. Even on a perfectly tuned machine the quality of the signal would degrade after several regenerations. In other words, on a repeating echo, the quality would change (degrade) with each repeat because this involved playing the first echo out, recording it again, playing it, recording that signal again, etc. The degradation happened fairly quickly (as opposed to the pure looping effects, which were one recording that just played back over and over).
Eventually analog and later digital devices were created that were in many ways better for doing delay effects. They were cheaper, more reliable, required virtually no maintenance and eventually sounded better in terms of the delayed signals being more like the original and not degrading. But by that time so many musicians and producers were accustomed to the tape delay sound that it was missed. Developers of digital delays had to put filters in to roll off high frequencies as echos repeated and so forth. Even with a modicum of parameters designed to help digital devices sound more like their tape-based ancestors, the difference was still significant. In more recent years the technology of modeling has allowed much more accurate emulation of these old techniques. When you see “tape delay” as one of the algorithms in your digital box or software, it’s probably referring to the emulation of these old sounds, and many of their inconsistencies. Still some purists prefer the sound of the old tape units. This is not unlike the arguments that exist for analog recording today: some of the deficiencies of analog recording actually produce a sound many people find desirable.