Trigger Editor

A MIDI trigger connects an incoming MIDI message — from a foot controller, expression pedal, or control surface — to an action in OnSong, so your hardware can drive the app hands-free. This screen sets up a single trigger. Your changes save as you make them, so just tap Done when you’re finished. Which options appear depends on the kind of controller you’re mapping, but every trigger starts with these two:

MIDI Event

A MIDI Event is the incoming message that fires the trigger — a note, a control change (CC), and so on. Tap to choose the message and its channel; the row shows your choice, like “CC 4 on Channel 1.”

Action

The Action is what OnSong does when the trigger fires. Tap to pick from the action chooser; the row shows the assigned action, or “Unassigned.” For a variable control change like an expression pedal or knob that sends a smooth 0–127 sweep, you’ll also see:

Response Curve

The Response Curve shapes how the controller’s travel maps to the action.

• Linear — the controller and the parameter move together, 1:1.
• Logarithmic — most of the travel works at the quiet end; great for a natural volume feel.
• Exponential — most of the travel is subtle, and the top of the range pushes hard.
• S-Curve — stable at the extremes and fast through the middle; good for crossfades.

Minimum and Maximum Value

These clamp the input event useful range within 0–127. Anything outside the range is ignored, so you can dial in exactly the sweep you want. The minimum always stays below the maximum.

For an momentary control, like a button or switch sending a CC, you’ll see these instead:

Behavior

Behavior decides how presses map to the action. Tap the row to cycle through:

• Momentary — active once a value great than 0 is received
• Latch — fires the action on both edges, but with no on/off value. Press fires it once, release fires it again, each just a plain action. Use it when your controller sends a separate press and release message and you want the action to respond to both.
• Toggle — treats the action as an on/off state. Crossing the threshold on the way up sends the "On" action while dropping back below sends the “Off” action. Use this for anything with a held state like a mute, a hold, a light.

Threshold

This is the value at or above which the controller counts as on. Values below it are ignored. It defaults to 1 for Momentary and 64 for Toggle.

Inverted

This setting reverses the input value direction. 0 becomes 127 and vice versa. Handy when a pedal is mounted or wired backwards.

Active

This turns the trigger on or off. Switch it off to suspend the trigger without deleting the binding, so you can bring it back later.