Surge XT's FM2 targets musical FM sounds; FM3 adds a fixed-frequency third modulator for inharmonic timbres

FM2 is a mini FM synthesizer with one sine carrier and two sine modulators. The modulator ratios are always integer, guaranteeing harmonic (cyclic) waveforms. The M1/2 Offset parameter detunes modulators by a small absolute amount, creating beating and slowly evolving timbres. Feedback modulates the carrier with itself. FM2 is designed for musical, pitched FM sounds. FM3 extends FM2 with three modulators whose ratios can be non-integer and whose third modulator has a fixed absolute frequency (in Hz), enabling inharmonic metallic, bell-like, or noisy timbres. Both oscillators have Vintage FM feedback mode for smoother, more analog-like feedback. Integer ratios produce harmonic spectra; non-integer ratios produce inharmonic/clangorous sounds.

Examples

FM2: M1 Ratio=2, M2 Ratio=3, moderate amounts — classic electric piano harmonics. FM3: M3 Frequency = 432 Hz (absolute) creates a non-tracking metallic undertone regardless of played note.

Assessment

What is the timbral difference between FM2 M1 Ratio = 2 vs. M1 Ratio = 2.1? In FM3, what happens to the M3 modulator’s pitch relationship to the carrier as you play different notes?