Many entities within the Symphony have access to otherworldly senses, collectively known as Symphonic resonance. These senses play a critical role in surviving the Symphony, allowing individuals to sense the presence and activity of their peers - and enemies.
The two senses are aetheric resonance and acoustic resonance. Not all entity types have both, and many find themselves having to work around the limitations of having only one or the other.
Aetheric resonance is possessed by Demons, cryptids, cryptoflora, allowing them to sense sources of and the expenditure of Aether.
Acoustic resonance is possessed by Demons, Pactholders, Angels, and stigmatics, allowing them to sense "acoustics", also informally known as spell sounds.
Not to be confused with:
Resonance, the strength of synchrony between a Pactholder and their Demon.
Sympathetic resonance, a property of hardware that describes how closely it aligns with a gadget's effect.
Demons, cryptids, and cryptoflora can sense Aether through a sensation known as "aetheric resonance". How this sensation manifests varies between individuals - some describe it as having a slow, uncomfortable pull, while others say it has a metallic scent or indescribable hue.
The God Machine's most potent endeavors are dependent on the conversion of Essence into Aether, from Angelic Numina, Influences, Manifestations, true forms, to facilities and stockpiles. The Unchained find aetheric resonance as a valuable asset to navigate the Symphony - and luckily, angels have no comparable abilities.
A demon spends 1 Aether to open up their aetheric resonance in a radius around them, which goes through physical structures. They become immediately aware of all sources of Aether, including other demons, stockpiles, and facilities. They are able to tell the distance and quantity of Aether, relatively speaking, such as "a massive energy source is approaching from due east", or "there was a brief flicker of Aether being used to the north".
Angels in Twilight are still vulnerable to aetheric resonance. However, Demons and Angels hidden by Cover are not pinged by this sense until they expend Aether or Essence.
Note that Aether is an impersonal energy, identical in feeling regardless of origin. This makes aetheric resonance a poor tool for judging specifics of an Aether source.
1-2 ❖ 5 yards, same room, small apartment
3-4 ❖ 50 yards, multi-story home, concert hall
5-6 ❖ 500 yards, office complex, entire city block
7-8 ❖ half a mile, skyscraper, entire neighborhood
9-10 ❖ 1+ miles, sprawling industrial complex, massive estate
Cryptids and cryptoflora substitute their Rank for Primum to determine their aetheric resonance radii.
Interestingly, cryptids, cryptoflora, and stigmatics do not register on aetheric resonance, even if their abilities expend Aether - Symphonic scholars theorize that their warped forms straddle the line between reality and Symphony in a way that naturally masks them.
All Symphonic entities with acoustics, an identifying supernatural signature generated by spells, are able to "hear" them in turn through "acoustic resonance". Angels, demons, pactholders, and stigmatics have acoustic resonance, while cryptids and cryptoflora do not.
As acoustics do not cause actual soundwaves, this sense persists even if the individual is physically deafened. Additionally, acoustics travel through mundane structures and obstacles without hindrance, allowing individuals to hear spell casts even through walls or the ground.
Acoustic resonance is a passive sense that cannot be turned off. Understanding it requires the knowledge of two concepts: the dynamics radius and the acoustic resonance radius.
The dynamics radius describes the radius around the spell caster. This radius is fixed depending on the type of spell, regardless of the caster's Resonance or Primum.
The acoustic resonance radius describes the radius around an individual in which they can sense acoustics, comparable to a demons' aetheric resonance radius. Demons, Pactholders, and Angels have scaling radii based on their level, while stigmatics have a fixed radius.
Acoustic resonance is triggered whenever there is any overlap between a dynamics radius and an acoustic resonance radius. Unlike aetheric resonance, however, the listener does not get a sense of direction nor distance - but due to the unique nature of acoustics, this sense is personal and allows for identification. Some individuals are able to hone this sense in order to get a very vague direction - such as "somewhere north" or "to the southeast", but it is impossible to gain more detail.
❖ Etude: 10 yards
❖ Leitmotif: 20 yards
❖ Cadenza: 30 yards
❖ Angelic Numina/Influence: 5 yards
❖ Angelic Incepts: 50 yards
❖ Demons/Pactholders: 5 yards per Primum/Resonance
❖ Angels: 10 yards per Rank
❖ Stigmatics: 10 yards