Behringer HALOS: Physical Modelling Resonance in Eurorack – An Analytical Dive

HALOS is introduced as a physical modeling synthesizer for Eurorack, purpose-built to bring the resonant qualities of strings, membranes, and tubes into modular setups. Rather than acting as a conventional oscillator, HALOS is a resonator that employs physical modeling synthesis to turn both internal and external unpitched signals into rich, pitched sounds. The video highlights its ability to conjure everything from plucked and strummed instruments—think harps, slide guitars, and sitars—to mallet-based tones like xylophones and tubular bells. This approach makes HALOS a versatile tool for creating organic, evolving soundscapes that respond dynamically to the nuances of modular triggers and envelopes.

HALOS features three distinct resonator engines, each accessible via a colour-coded LED. The green mode, known as the modal resonator, simulates the resonance of vibrating structures such as bars, plates, and strings when struck—ideal for recreating percussive and mallet-driven timbres. This mode is particularly adept at producing the metallic and woody tones characteristic of classic physical modeling.

Switching to the yellow LED brings up the sympathetic strings engine, which focuses on the behaviour of strings that are plucked or strummed rather than struck. This mode excels at generating lush, overlapping harmonics and the subtle interactions found in acoustic string ensembles. Finally, the red mode introduces a non-linear, inharmonic strings engine. Here, comb filtering and absorption filtering are combined with non-linearity and a dispersion all-pass filter, resulting in timbres reminiscent of harpsichords and metallic bells. Each mode offers a unique palette, encouraging experimentation with both traditional and unconventional sound sources.

HALOS brings pseudo-polyphony to Eurorack, a rarity in modular environments. Three polyphony modes are available: monophonic (green), two-note overlapping (yellow), and four-note overlapping (red). In monophonic mode, each new note cancels the previous, maintaining classic modular behaviour. The two-note and four-note modes, however, allow for overlapping notes, creating evolving textures and more complex harmonic interplay. This approach is particularly musical, lending itself to both melodic and ambient applications.

Parameter control is comprehensive, with dedicated knobs for frequency (pitch), brightness (harmonic content), damping (decay time), position (excitation point), and structure. The structure parameter adjusts partials in the modal mode and detuning in the sympathetic and non-linear modes. This level of control enables nuanced shaping of timbre and dynamics, making HALOS responsive to both subtle modulation and dramatic performance gestures.

The video closes with tantalising hints at hidden features lurking within HALOS. Beyond its primary resonator engines, the module reportedly houses a secret FM synthesizer, a reverb, and even an organ string machine inspired by the Roland RS09. These extras are not demonstrated here but are promised for exploration in part two. For now, Behringer leaves us with the sense that HALOS is more than meets the eye, inviting further investigation from adventurous modular users.