For those who don't understand French, here's the Google translation:
Geronimo ^^
The explanation is very simple.
The use of the THRU Pass is to hear the sound that passes through this rack extension when you do not press play, or that the same rack extension is not triggered by another utility such as the pattern Matrix "of reason.
For example, create a Dr.Octorex, then create a SideChain ReAction (no new rack extension, directly wired to the audio output of Dr.octorex). When our sequencer is stopped (no "Play") if we want to hear our Rex loop, Pass THRU "must activate and we will hear the sound without effect.
Finally the Pass Thru function acts a bit like a Bypass for the module. The advantage of this is that whenever you want to work on our basic sound (no effect), you just have to do "stop" in our sequencer, then once our sound adjusted more than Restart our song with "Play". A huge time saving instead every time either to make bypass / on the extension rack for example
To elaborate further, PASS THRU allows SCRE to have 2 modes. The mode when PASS THRU is ON allows the original signal to 'pass thru' unaffected, until SCRE is triggered, so this is good for say ghost triggers (ala ghost kicks / snares etc) to duck the signal when the trigger is playing - very much like sidechaining into a compressor. When PASS THRU is OFF, you get no dry signal (when mix is at 100%) but when SCRE is triggered whatever audio is being fed into SCRE at that time will be processed and volume ducked. This is so that you could have SCRE as your defining volume control when doing sound design
For example:
◙ In a Combinator, add a Thor followed by SCRE.
◙ Set Thor's Mod Matrix so that 'LAST KEY' is rigged to CV out 1.
◙ Loop that CV out 1 to SCRE ALL CV in.
◙ Turn on SCRE PASS THRU to OFF.
◙ Turn on SCRE ALL LOOP, RETRIG and RELEASE.
Now when Thor plays for example a lead or pad sound, SCRE will do the volume controlling of the sound and triggers only when MIDI is on. Since Thor is 'listening' always for the Last MIDI key, you can play chords because you have more than 1 key down. This in turn now makes SCRE a performance tool, which can be time sync'ed to your BPM, but will trigger only when the first note is being played.
We'll look at making some videos to show this, there's a couple of patches that do this already in the SCRE presets