Blind Mode

Blind Mode is you telling Fusor Studio to keep sending and stop listening. Normally Fusor Studio sends control changes to the DJ app and listens for deck state (play/pause, volumes, tempo, crossfader) coming back. In Blind Mode it still sends everything, but ignores anything that returns.

Use it when the DJ app doesn't send MIDI feedback (djay Pro most notably), when no DJ app is running at all, or when you just want to rehearse transitions without telemetry in the loop.

You are the only thing that turns it on. Fusor Studio never switches to it on your behalf, and it is off again every time you launch the app.

When to use it

You're mixing with djay Pro or another app with one-way MIDI.
Your MIDI mapping sends controls but doesn't return deck state.
The host DJ app isn't running and you want to rehearse transitions.

If your DJ app sends full state (Traktor with the standard mapping, for example) and is running, leave Blind Mode off.

Turning it on and off

Click the App menu in the player's top-left corner and toggle Blind Mode.

It does not persist. Every launch starts with Blind Mode off. It's a decision about the session in front of you, not a preference to carry forward.

Turning it off runs a fresh capture automatically, because the control baseline you were using while blind was a stand-in rather than anything read from the DJ app. If you're armed and waiting when you turn it off, that capture waits until you disarm, rather than interrupting a transition that's about to start on its own. While it waits, the status line carries a RECAPTURE PENDING — prefix in grey, so you can see the refresh is owed. See The Player Window for how that prefix reads against BLIND and UNCAPTURED.

Changing the MIDI bus turns it off for you, and says so on the status line. Blind Mode is a judgement about one particular setup; once you point Fusor Studio at a different bus, that judgement is out of date, so it goes back to listening and captures from the new bus straight away. This is the one thing that switches it off without you asking, and it can only ever make Fusor Studio listen, never make it run blind. If the new bus is also silent, the capture fails and offers you Blind Mode again, exactly as it would at launch.

What happens when capture can't reach the DJ app

When Fusor Studio asks the DJ app for its control positions and gets nothing back, it tells you and stops there. It does not switch modes for you. The status line names the failure (Capture failed: no telemetry or Capture failed: no deck state) and arming stays blocked, because without a baseline Fusor Studio can't restore your controls after a transition.

From there you have two ways forward:

Fix the return path and run Capture Control State again from Settings → Connection. This is the right move if you expected telemetry to work. See Troubleshooting.
Turn on Blind Mode and carry on without telemetry. Fusor Studio sets a default baseline so you can arm and run.

The same applies with no DJ app configured: capture is skipped, arming is blocked, and the status line points you at Settings. Choosing an app runs capture automatically.

Requesting a capture while Blind Mode is on is skipped, with a note saying so: there's nothing to observe when the bus is muted.

It disables the parts of Fusor Studio that need to read DJ app state. Most of it is transparent; transitions arm, start, and run as normal. A few features need state and are unavailable:

Disabled

All inbound telemetry. This is a literal blackout. Deck-playing state, volumes, tempo, and crossfader CC are all ignored at the MIDI entry point. The principle is "no telemetry means no telemetry for anything." If you can't fully trust the DJ app's state, don't trust any of it.
Manual Run Mode. Without crossfader CC there's no input to drive progress. Blind Mode forces Auto Run Mode on entry and locks the Mode toggle at Auto. The toggle stays visually lit (Auto is on) but clicking it does nothing functional; the status bar explains.
Deck-playing guard. Transitions can Ready and Start without the outgoing deck reporting "playing". Fusor Studio assumes you've started the track.
Snapshot / Restore. Fusor Studio captures pre-transition control positions and restores them when a transition completes. Without telemetry there are no pre-transition values to capture, so restore does nothing. Controls stay where the transition left them.
ERA (curve adjustment) and per-control soft takeover. With telemetry, Fusor Studio adapts the start of a transition to where the controls actually sit: if the crossfader is already at 50% when a transition starts, it picks the curve up at 50% rather than snapping back to the authored start. Without telemetry it can't see where any control is, so this adaptation is off. Every control starts at its authored value, including the crossfader. If your crossfader is at 50% and the curve's authored start is 0, the next CC sent will be 0; your hardware soft-takeover (or a careful hand) needs to handle the jump.
Manual takeover detection. Even if the DJ app sends crossfader CC, Fusor Studio ignores it here, so it won't auto-detect when you've grabbed the crossfader mid-transition.
Tempo Ramp. The Tempo Ramp button is disabled and shows a tooltip. A fusor containing a TempoRamp phase refuses to arm, since the ramp needs to read the deck's actual tempo fader position.
WAIT_UNTIL action steps. These fail fast with an error rather than timing out silently. WAIT_UNTIL watches a state value Fusor Studio isn't receiving.
Role resolution from deck state. Fusor Studio can't pick incoming/outgoing decks by watching volume faders. Use Capture Control State to detect roles, or set them with the Swap button.
The tempo polarity test in Guided Setup. It exists to check whether telemetry works, so it asks you to turn Blind Mode off rather than quietly switching it off for you.

The blackout is total, with no carve-outs. If you have a working bus, stay on telemetry. If you don't, go blind and use Auto Run Mode.

Arm button behaviour

Blind Mode leaves one way to start a transition: the press-Play default. The Arm button shows PLAY, and pressing it arms and starts in one press. The Start-with-Incoming opt-in is disabled here, because waiting for the incoming deck to start means watching telemetry. See Start-with-Incoming for what that does to a preference you already had set.

Completion

Transitions auto-complete at 100%. There's no deck-stop telemetry to wait for, so the engine finalizes on its own. The "reach 100% but stay live" behaviour from Manual Run Mode doesn't apply, since Manual Run Mode is unavailable here.

Completion is completion: deck roles swap on their own, exactly as they do while Online. Manual Role Swap is there for the cases where the roles end up wrong (an aborted transition, or a track you swapped by hand), not as a step you have to remember after every run.

Status line

While Blind Mode is on, state text is prefixed with BLIND – in grey, for example BLIND – Unarmed. Grey rather than red, because the missing telemetry is intentional rather than a fault.

djay Pro sends controls out but does not send deck state or tempo back over MIDI. Blind Mode is the supported way to drive it from Fusor Studio:

Set up your djay Pro MIDI mapping to receive Fusor Studio's output. (Crossfader feedback from djay Pro is ignored here, so you don't need bidirectional crossfader, and Manual Run Mode isn't available either way.)
Click the App menu in the top-left of the menubar and turn Blind Mode on. Remember to do this each session — it doesn't carry over from last time.
Build fusors without TempoRamp phases or WAIT_UNTIL steps; they will refuse to run.
Arm and fire transitions as normal. Fusor Studio won't block on deck-playing state, and manual takeover won't auto-trigger.
Roles swap automatically when a transition completes. If they end up wrong, after an abort or after you reload decks by hand, click the Swap button in the menubar to flip them. See Manual Role Swap.

Tips

If you build a fusor that needs TempoRamp or WAIT_UNTIL, test it against a two-way mapping (Traktor, for example) before relying on it blind. Those phases won't run.
If capture fails at the start of a session, that's Fusor Studio telling you the return path isn't working. Worth thirty seconds of checking before you reach for Blind Mode, especially if it worked yesterday.
If you're debugging a mapping and not sure whether Fusor Studio is receiving state, leave Blind Mode off and watch the status line. It tells you what Fusor Studio can see. (In Blind Mode the bus is intentionally muted, so the line won't respond to incoming MIDI.)