executor

A person who carries out some task.

This manner can no longer be considered "folk-song," yet neither can it be taken as "art-song," at least not conscious art, for the executors, the chazzanim, did not know of any theory of music and modulation.

A component of a system that executes or runs something.

When searching for a solution is unnecessary, then the program executor "doesn't care" which solution is generated nor how it is obtained.

Someone appointed by a testator to administer their estate in accordance with their will; an administrator.

literary executor

An executioner.

The sad-eyed justice, with his surly hum, / Delivering o'er to executors pale / The lazy yawning drone.