Lithoform Engine + Corridor Monitor + Chromatic Orrery + Panharmonicon

Lithoform Engine

Corridor Monitor

Chromatic Orrery

Panharmonicon

How it works

1. Cast Corridor Monitor for 2.
2. With Corridor Monitor on the stack, use Lithoform Engine to copy the spell, using Chromatic Orrery to pay for Lithoform Engine.
3. Let the copy of Corridor Monitor resolve, triggering Corridor Monitor twice due to Panharmonicon, untapping Chromatic Orrery and Lithoform Engine.
4. Repeat steps 2-3.