Harmonic Core System

A Harmonic Core System is essentially one or a series of devices acting as a sort of personal sub-server for a Cross-Ley's (see Leyaloids and Cross-Leys) given server registration. They allow for more than one song "program" to be run at one time, enhancing the power and control of song magic. Once a Core is assigned to a person's registration, it can be programmed with a variety of custom features, such as activating sub-songs as a chain reaction to a regular song magic, running extra functions during a song, alerts (think being able to debug your songs as you craft them), or implanting your own words and bits of language (which can be a bit of a pain due to the need to define every new term or link it to a Melodicode synonym).

Core Song Name Formatting

While song magic run through regular Harmonic Servers has a very simple naming format, song magic processes run through Harmonic Cores have a more complex naming structure to prevent interference with actual server magic. It looks something like this:
ardhanarishvara.COREX_index.UNION::HARIHARA;
This particular Core Song is from Sal Turran, the creator of the Core Systems themselves.
The first socket, in this case "ardhanarishvara", is a programmed signifier that acts as a shorthand or redirect for the Cross-Ley's server registration. Only one signifier can be had per person per system, but the same person can have another signifier that connects to a different core system. COREX is a structural piece that indicates that the song is a Core Song that is being sung by one singer and affecting the environment outside- in other words, the type of Core song. There aren't any other types of Core Songs at this point, however.
The next segment and its accompanying socket, "index.UNION", indicate the Melodex song (or regular internal song magic) that is activating the sub-program of the Core Song. The final socket, "HARIHARA," is the name of the Core Song itself that you'd use to indicate the program being run.
In other words, you could break down a Core Song's name format like this: "Registration Ardhanarishvara activates Program Harihara alongside Melodex Entry Union."

Example Uses of Core Systems

The creator of the Harmonic Cores has some examples of what they use their cores for, along with their corresponding names:
ardhanarishvara.COREX_index.CLARION::PRANABEAM;
When Sal sings their Clarion song magic, which has the effect of dropping wave-like projectiles from above, the program Pranabeam adds additional beam projectiles fired from the area around the Core itself.
ardhanarishvara_01.COREX_index.MEDITATION::REFINEMENT;
ardhanarishvara_02.COREX_index.MEDITATION::SYSTEM=ALERT;
ardhanarishvara_03.COREX_index.MEDITATION::ALERT=SYSTEM;
Notice the new bit of formatting by the signifier socket, which indicates that multiple cores are being accessed for this set of songs. The original Melodex song that activates the trio is Meditation, which puts one target in a sleepy state for introspection and healing. Refinement allows Sal to pick through their feelings and craft songs more precisely. System Alert and Alert System have different functions despite their trollingly similar names. System Alert produces notifications for Sal when various parameters are reached during songcrafting, while Alert System saves data and terminates the whole sequence if someone enters the area without Sal's permission, allowing them to respond to intruders (and, once, a stray dog).

Impact of Core Systems

Currently, Harmonic Core Systems are very difficult to obtain, build, and properly program. Generally, those who own Core Systems received them as a gift from the creator. Since they're a relatively new invention and limited to the upper echelons of song magic users, not many people even know they are an option for song magic control.
There have been reports of some upstarts attempting to build their own, but they have encountered a variety of hitches preventing successful creation, such as a failure to connect to their regular server registration, or improper programming or construction leading to unintended effects. Still, the ability to add programmed effects to one's song magic (the creation of which can be a bit unpredictable) separate from a main server is a powerful addition to the world of Song Science.