3. Instruments and sound design

Every instrument in the browser is a ready-to-play sound built on Nebula's own modular synth engine (or, for FM, its own four-operator engine) — there is no separate "load an instrument" step. Click one in the browser and it is live on the instrument screen.

The built-in instrument categories

The INSTRUMENTS tab groups everything by kind:

• SYNTH — Lead, Square Lead, Soft Pluck, Glass Bell, Acid Saw.
• BASS — Bass, Sub Bass, Growl Bass, Square Bass.
• PAD — Pad, Warm Strings, Glass Pad.
• DRUMS — a drum kit built from modules, and the Drum Rack (chapter 4).
• SAMPLER — the Sampler (chapter 4).
• FM — six FM synth presets (below).

Every one of these plays polyphonically (multiple notes at once) and responds to velocity (how hard a key is pressed or how loud a note is written).

The macro knobs

Rather than exposing every raw modular parameter, each instrument's screen shows a small, consistent set of macro knobs that shape the sound without needing to understand the graph underneath — typically Volume, Brightness, Resonance, Attack and Release. Brightness and Resonance drive the filter (how open/dark it sounds, and how much it "sings" around the cutoff); Attack and Release shape how a note fades in and out.

What is under the hood: the modular engine

Nebula's own instruments are built from a small set of modules, wired together into a patch:

Module	What it does
Oscillator (VCO)	The raw tone: sine, triangle, sawtooth or pulse/square waves
Filter (VCF)	Shapes the tone's brightness — low-pass, high-pass or band-pass, with resonance
Amplifier (VCA)	The volume stage, usually driven by an envelope
Envelope (ADSR)	Attack/Decay/Sustain/Release — how a note's level changes over time
LFO	A slow, cyclic modulation source (vibrato, filter sweeps, tremolo)
Noise	White/pink noise, for percussion and texture
Mixer / attenuverter	Combine and scale signals

This is real-time, sample-accurate audio synthesis, not sampled/recorded instruments — every note is generated fresh. A future visual patch editor will let you build your own instruments from these same modules; today the factory instruments are ready-made starting points.

The FM synth

The six FM presets — FM E-Piano, FM Bell, FM Bass, FM Brass, FM Pad, FM Organ — use a different engine: four operators (simple sine waves) that bend each other's pitch very fast, which is what makes FM (frequency modulation) synthesis sound like bells, electric pianos and brass rather than plain, static tones.

On a track playing an FM preset, the FX view of the instrument screen shows the FM card:

• Eight numbered algorithm buttons choose which operators bend which others; the operators marked OUT are the ones you actually hear.
• Four general knobs: Feedback, Gain, Release, Tune.
• Per operator (four columns): Ratio (how many times faster than the note it vibrates — whole numbers sound harmonic/organ-like, odd or fractional ones sound metallic/bell-like), Level (how loud it is, or how strongly it bends the next operator), and an envelope: Attack, Decay, Sustain.

Turning any knob here applies immediately (you hear it on the keys right away) and is one undo step; your changes are saved with the track, on top of the preset you started from.

Effects on an instrument

Every track — whatever instrument it plays — can have its own chain of effects. That is chapter 5. The next chapter covers the two "bring your own sound" instruments: the Sampler and the Drum Rack.