Back in the day when us budding guitarists were trying to learn tunes and licks from recordings, there weren't any Youtube tutorials, isolated tracks, on-pitch time shifters or online tabs... nothing. All we had in our world were our ears and hopefully a really good guitar teacher to point us in the right direction.
I remember, early on in my playing, coming across certain guitar licks that sounded almost physically impossible to play. They were just too smooth sounding, with notes in incredibly intricate sequences.
My first exposure to this sound was on Yngwie Malmsteen's iconic "Blackstar," during the improvised solo directly following the acoustic intro. I simply had zero idea how this was done. Van Halen's "Cathedral" also had this sound.
Luckily, one of my guitar teachers knew exactly how to get it and told me it was produced using a delay pedal, but the notes had to be played in a certain rhythm and tempo with the delay to achieve the effect. So I ran out that day and got a delay pedal, it ended up being the BOSS DD-2, the world’s first digital delay in a stompbox form.
That incredible echo sound was achieved when playing straight notes, like a basic quarter note pattern, but timing it so the 1st "echoed" note would fall in between the 2nd and 3rd played note, creating a dotted 8th note rhythm (not an exact analogy, but think a horse's gallop/"William Tell Overture" type rhythm).
More examples of this great technique would be Paul Gilbert's "The Echo Song", Nuno Bettencourt's "Flight Of The Wounded Bumblebee", Cacophony's "Desert Island" solo (at 3:05) and Buckethead's "Big Sur Moon," it's all really beautiful stuff.
Now for the solo on MaelstroM's "13 Within A Circle." I employed this echo technique with a "call and response"