It's  the Engombi album. It came out in 1997. Somono was already in Quartier Latin. He only left in  1998.

Did Koffi let him participate?


You can hear him here for instance :

Quartier Latin spent at that time 8 months in Europe (December 1997 to August 1997. In November 1997, Koffi came back with a small part to finish Loi.

Artists are always free to help other musicians on albums and nzong/nzings, except if it it’s their own project, then they will risk to get fired or suspended. In 1998 for example Mboshi, Babia Ndonga and Eric Tutsi helped Alpatchino with his album Offensive Generalise. The same year Popolipo, Champion, Do Akongo and Somoni helped Cesar Loboko with his solo album.