The Bypass (B) button at the left-hand side of the Master Effects layer provides a way to simultaneously deactivate (bypass) the entire layer.
When you click the master “B” button, the button and the title-strip of the Master Effects layer will change color like this:
Click the “B” button again to change it back and un-bypass the layer.
Note this “layer bypass” is unaffected by the bypass state of the individual effects. Suppose you had three effects on the Master layer, and the middle one was bypassed. You could bypass the entire layer, then un-bypass it, as many times as you want, and that middle effect would remain bypassed.
The Master Effects layer-bypass function is there for two very different reasons. First, it provides a quick way to toggle the layer on and off, so you can hear how much the Master Effects affect the sound of your patch. In general, it's good practice to avoid doing anything too noticeable on the Master layer; it's mainly there for “mastering” effects like EQ and compression/limiting. More dramatic effects like distortion, delay, and reverb should ideally be placed on Aux-Effects layers.
The second and more important purpose of the Master bypass is that Unify can activate it automatically for any patch you load into an embedded Unify instance. Suppose you have loaded a nice rhythmic pad, e.g. a “BPM PAD” or “BPM KEY” type patch, whose Master layer has the typical “master optimizer” chain of FlexEQ (equalization), Restrictor (compression), and LoudMax (limiter). To make the rhythmic aspect much stronger, you decide to add a “BPM DRUM” patch, loaded into a new embedded Unify layer. This new drum patch has a similar chain of “master optimizer” effects on its own Master layer. This leads to a subtle problem: the drum patch will now go through two FlexEQ's, two Restrictors, and two LoudMax instances, and as a result, won't sound exactly as it was designed to sound.
Starting with Unify v1.3.2, Unify will automatically bypass the Master Effects layer of the embedded Unify patch. The result will then sound exactly the same as if you added the patch's MIDI, INST, and AUX layers to the main patch. The sound of those layers will not go through a double Master-effects chain, and hence the embedded patch will sound the way it was meant to sound.
In a “compound” patch (one which contains embedded Unify instances), you can open the embedded Unify's GUI and switch off the Master-layer Bypass button if you wish. If you then save and re-load the compound patch, it will re-load exactly as you left it, with the embedded Unify's Master layer NOT bypassed.
For patches you create yourself, if you want to ensure that the Master Effects layer is never automatically bypassed (e.g. because you have put “creative” effects like delay on it), check the “Lock Master Effects” box at the bottom-left corner of the Save dialog.