Looked at previous threads WRT 'the abba sound'

Gang -- I'd been reading other threads on this board, and noticed a thread 'dear' to my heart -- the abba sound.  Didn't want to follow directly with that thread since it is long dead, but I might have something to offer.   Even though my 'restoration processor' has been helpful in decoding the ABBA sound, it really isn't the key step.   Geesh, even the Carpenters have used some of the processing that my processor can undo -- the compression isn't really the only key to 'the ABBA sound'.  I have a formula which is expressible with a SOX/shell script which can be helpful to see what they have done.   I am not going to provide it unless there is a lot of interest (it isn't long, but it is technical.)   The key has been related to applying a 90deg phase shift and a 10msec time delay.   The 90deg phase shift kind of allows mixing the sound in a way that it doesn't cancel, and the 10msec delay causes the very dense sound when summed back to the audio.  I haven't derived the exact formula, but I created a decoding version that does work in most cases (as you can hear by some of my examples.)   It is important to start with a pristine copy or the math probably won't work -- so the Polar releases or other obscure releases which weren't mis-processed are probably your best bet.  I have an ancient, non-english release which contains about the cleanest copies that I have heard -- and that is what I use, very likely because the cost of finalizing that version wasn't deemed to be worthwhile. I haven't tried the Polar release yet for the test.

Even though I don't know their exact procedure, it is probably like: (take the signal delayed to match the hilbert 90deg transform -- but don't use the transform), then (take the signal witih hilber transform PLUS 10msec), add the signals together -- and voila -- you have close to the ABBA sound.   I haven't checked the 'encoding' procedure, but I am using a similar inverse with good results.  These tests and associated scaling parameters take time to find out (by trial and error), so that is the only reason why I haven't provided an exact encoding script.

I am willing to share my decoding script, but undoing the general steps above are the way that I have cleared up the voices.  It is NOT fun using these tools, but it is nice to be able to hear the voices so clearly.

ADDON:  Just tried the Polar release -- there are some hiccups, but comes close to working okay.   The biggest problems is that they did some enhancement and some compression which messes up some of the math, but the algorithm still seems to apply.

John