When adding effects to a sound, it's not uncommon to want to apply these effects to just a certain part of the sound. For example, you might not want a complex chorus to affect your bass too much, or a hard distortion to totally fry your high end. Either way, multiband processing adds a dimension to effect chains that really opens up a new world of options in sound design. Multipass helps you with this, allowing you to split the input sound into up to 5 easily tweakable frequency bands and applying unlimited number of effects to each band. Pitch shifted auto pan with a filtered chorus delay distortion? Coming right up!
Band splitting comes with a bit of a price. It's unavoidable (without adding latency) to mess a bit with the phase of the sound. Usually this is not a problem, but when chaining multiple multiband effects this can add up to a lot of phase distortion. In Multipass, the band splitting is only done once no matter how many effects you add, leaving the phase as minimally harmed as possible. It also sorts out dry/wet mixing of effect lanes properly without phasing where possible. Parallel multiband compression, here we come!
While adding four filters a frequency shifter and a stereo width modifier can be interesting in itself, adding four filters with sweeping cutoff retriggered by audio threshold, a frequency shifter bound to the MIDI note and stereo width scaled by the input RMS can be… Well, probably strange. But it may be amazing, and trying it out is just a couple of clicks away. Try it!
When you're tweaking a specific frequency band, the other bands and effects involved can sometimes make it hard to properly hear what's going on. Mute or solo effect lanes to quickly home in on what you're doing. And if you automate it, it can even be an effect in itself!