Stereo and Panning

Audio cables in Throughline carry stereo. There is no separate left and right cable to patch, and no pair of ports to keep in step — one Audio Out connects to one Audio In and both channels travel together.

That keeps ordinary patching simple. Where it matters is at the points where the channel decision changes: when a mono source becomes stereo, when a stereo signal has to become mono, or when you want to treat the two channels differently.

How Channels Behave

• A mono source expands to stereo when it meets a stereo path.
• A stereo signal keeps its distinct left and right content through nodes that preserve stereo.
• Unconnected inputs contribute silence rather than noise or DC.

Mix follows all three rules: mono inputs expand, stereo inputs keep their content, and empty inputs stay silent. You can feed it any combination without thinking about channel counts.

Some effects produce stereo from a mono input by design. Chorus widens and delivers the result through Audio Out. Delay can run ping-pong repeats across the field and delivers them through Stereo Output.

Placing a Signal

Pan sets stereo position. Pan runs from -1 at full left through 0 at centre to +1 at full right, and Pan CV accepts a control signal so position can be modulated — an LFO into Pan CV gives auto-pan.

For a mono input, Law chooses how the signal is distributed between the two channels:

• Equal power holds perceived loudness steady as the signal moves across the field. This is the usual choice for placing a sound in a mix.
• Linear uses a straight left-right gain change and is quieter at the centre.

For a stereo input, Pan acts as a balance control: moving left attenuates the right channel, and moving right attenuates the left. Law does not change that stereo balance behaviour.

Splitting and Merging

Use these when you want the channel decision recorded in the patch instead of left implicit.

• Stereo Split takes a stereo input and gives you separate Left and Right mono outputs.
• Stereo Merge takes mono Left and Right inputs and produces one stereo output.

Stereo Merge rejects a stereo signal wired directly into either input. Reduce or split it first — the node will not silently fold a stereo signal down for you, because that choice belongs in the patch where you can see it.

Reach for this pair when you want to process one side differently from the other, or before a mono-only destination where you would rather choose which channel survives than accept a default.

Common Patch Examples

Auto-pan

1. LFO set to bipolar → Pan Pan CV.
2. Source audio → Pan Audio In → Audio Output.

graph LR
    SRC[Source] -->|Audio| PAN[Pan]
    LFO[LFO bipolar] -->|Pan CV| PAN
    PAN -->|Stereo Audio| OUT[Audio Output]

Bipolar polarity swings both sides of centre. A unipolar LFO would only ever pan one way — see Modulation and Envelopes.

Process one side only

1. Stereo source → Stereo Split.
2. Left → Gain to trim or boost that side. Right → straight into Stereo Merge Right.
3. Gain Audio Out → a second Stereo Split. Its Left → Stereo Merge Left; leave its Right unconnected.
4. Stereo Merge → Audio Output.

graph LR
    SRC[Stereo source] -->|Audio| SPLIT[Stereo Split]
    SPLIT -->|Left| GAIN[Gain]
    SPLIT -->|Right| MERGE[Stereo Merge]
    GAIN -->|Audio Out| RESPLIT[Second Stereo Split]
    RESPLIT -->|Left| MERGE
    MERGE -->|Stereo Audio| OUT[Audio Output]

Gain has statically stereo audio ports: the mono Left signal expands when it enters Gain, and Gain's stereo Audio Out cannot connect directly to Stereo Merge's mono input. The second split makes the channel choice explicit again before the merge.

Widen a mono voice

Stack detuned copies at the source instead of widening afterwards. Oscillator has Unison Voices, Unison Detune, and Unison Spread built in — see Polyphony and Voices. Follow it with Chorus only if it still needs movement.

Rules of Thumb

• One Audio cable carries both channels. Do not look for a second one.
• Use Equal power or Linear to choose how a mono sound is placed. Stereo input always uses balance behaviour.
• Split and merge when the channel decision should be visible, not implicit.
• Stereo Merge will not accept a stereo input — reduce it explicitly first.
• Width at the source usually beats width added at the end.