Filmed later the same day as Waterloo and directed by Lasse Hallstrom on the same miniscule budget, this PROMO included musicians Lasse Wellander on guitar; Thomas Rydberg on drums (definitely not Ola Brunkert as I first thought) and a Pär David Johnson on bass. At this point, Lasse Wellander hadn't even debuted on an ABBA recording (his first would be working on Intermezzo No. 1 later in the year).

Benny "played" the same piano as in the Waterloo PROMO. 

Lasse, Thomas and Pär (along with future ABBA live guitarist and harmonica player Mats Ronander), were in the group Nature.

This is the 1974 single remix. A different version was overdubbed onto this clip for the ABBA Video Biography video from 1989.

For the 50th Anniversary in 2023, the PROMO was remastered and the 1973 version was dubbed into it, rather than the 1974 remix it was made for.  Ring Ring was made for distant countries like Australia, where the remix single was scheduled for release in July 1974.

ABBA - The Definitive Collection booklet written by Carl Magnus Palm; thanks to Ken Griffin, Ian Cole and Stuart Kerry.
YouTube link c/o AbbaVEVO