Mellotronists

A while back, we discussed the whereabouts and state of affairs of
the Polar AB Studios 'tron.  This made me wonder why "that" sound 
isn't on any ABBA recording.  Does anyone on our esteemed list know 
what sounds Mssr. Andersson used?  No evidence of 3-string, flute, 
choir, etc. on any ABBA recording I have but it's in the credits.....

FS. Weller   

(no 'tron yet but with 16,000 records, I even have that Barry 
What's-his-name around here somewhere!)