The band is called L'Agora. Unfortunately there isn't any information about them on the in Internet. I also asked myself these questions when discovering the song
Apparently Brazzaville had copycat of each famous group from Kinshasa back in the days. Here are other groups that simply were another from brazzaBilengue sakana=Empire Bakuba Moziki la Juventus= zaiko langa langaViva mandolina = anti choc bozi boziana Extra musica bonk= a mixture of zaiko and wenge