Mystic traces left behind by magick. The kind of magick used & the intentions of the mage affect Resonance. Mystic forces can also cause Resonance. Revised Edition & Mage20 state Resonance comes not only from magic but also the emotions of ordinary people. Resonance was not given solid rules before Revised ed core. Revised Ed. Resonance rules are clarified pg. 122 Fallen Tower. Mage20 gives basic info on pg. 560. Book of Secrets gave updated & detailed rules pg. 128-138. I treat Resonance like Paradigm in 1st Edition: allow STs to decide for themselves whether or not they want to use it in their games & to what degree.
First appeared on pg. 9 of Loom of Fate. Next on pg. 139 of Book of Chantries. First time it was applied to mages & their magick was pg. 112 Book of Shadows.
Resonance is sensed with Prime Sphere. Resonance can give away a mage that is trying to hide or lay low.
See Synergy