An amplified cactus is a cactus plant (preferably a Denmoza or Geohintonia) used as a musical instrument. It harnesses the acoustic properties of a cactus by applying contact microphones and amplifying their projection and tone.
Madness string 102496
It's a side effect of teaching. When you spend a large amount of time explaining things to people, especially the same thing over and over again, you eventually just try to find new ways to say it so you don't bore yourself to death.