She had worked with many different artists even before Kalafina, namely Kaori Hikita (3 songs) Mika Arisaka (2 songs) Marina Inoue (2 songs) and also all these gundam character songs, and with Saeko for whom she did 2 whole albums. Its was after seeing Kalafina success and how her lives were going that she united the 4 FJ girls into 1 unit, but still kept Yuuka kinda separate.
I dont know how she is thinking it, because for me as a fan either she makes the song as FictionJunction + singer or under the singer's name (eg Kaori's Calling, Keiko's Yuuyami no uta and Nanairo no Finale, or LiSA's YK songs after "from the edge") the result is similar.
Holy moly, i found a
Calling Live as per YT recommendation
https://www.youtube.com/watch?v=flcI2Pq0uKY