This one piqued my OCD, but then I had to set it aside for a stretch.  I had tried several algorithms, and many of them seemed to be missing ‘something’.  For example, Tape Delay modulation(s) were too fixed and regular.

Best (preliminary) results were with SpaceTime.  The delays are based on Vintage Delay (but no control over the bit depth).  They can be routed in series to the reverb for some smearing & slight diffusion.  Not too much – it’s a Plate.  Just a touch with no-dry Delay Level, shorter Decay, experimenting with Size to taste.

The Modulation there has a wider Rate range and incremental Depth fine-tuning.  Love this modulation fairly deep on its own, but in this case, subtle.  It’s the first effect in the chain, and the LFO can be made to sound semi-random / multi-waveform.

I believe I got the best Feedback results from FB:2 (past 12:00), but I went back & forth between both flavors.

I’ve since read somewhere (Keeley himself ?) that the Halo setting isn’t strictly locked to dotted eighths & quarters.  The comment got me wondering if that isn’t the ‘secret formula’.

I haven’t tried this, but it makes theoretical sense:  Let’s say it’s close … 360 ms. & 510 ms. @ 120 BPM.  The delays start out sounding like dotted 8th & 1/4, then gradually begin to drift apart, and clash with each other in the Feedback loop.

Just a theory at this point, but that might be the missing link in the Halo emulations here.  I’m going to try that out when I get back to my evil laboratory.