how do I create phasing between two audio like Steve reich's "Come out"
Im using two groove and basically adding and subtracting minimal amounts like 0.001 on both sig~.
I'm not sure if this is correct.
I wonder how others would approach to make more phasing effect.
Try looping the same section of one buffer in both players, keeping one speed at 1 and setting only the other to 1.001. The groove~ reference defines 1 as normal playback speed. With equal loop lengths and neither player being retriggered, that speed difference lets their playback positions drift apart rather than holding a fixed delay. I haven't tested your patch, so this is a simple comparison to try rather than a diagnosis of what it currently does.
I am looping the same part.
Is it not good to change both ? like if one gets + 0.001 other gets -0.001, using the !- object.
Yes, you can change both speeds around 1. With speeds of 1.001 and 0.999, the difference is 0.002, twice the difference between 1.001 and 1. Keeping one fixed was just a simpler comparison, not a requirement.