Ah, I should also add that I assumed you were asking about instrument auto vibrato. That has a resolution of 1/64th of a semitone, no matter if linear slides are enabled or not (which results in the +/-23 cents I talked about). The pattern effect (4xy) has a resolution of 1/8th of a semitone in linear slides mode, so at the maximum depth (15) it spans approximately +/-2 semitones. When linear frequency slides are disabled however, the depth indeed changes depending on which note you play, like in the MOD format. Expressing that in a formula is rather complex as it requires explaining the entire concept behind pitch in the MOD format. Before I start digging into that, let me know if that is actually relevant for you or if linear slide mode is enough to know about.