Let us attend! Let us stand aright! Let us stand with fear!” and all of the faithful angelic heavenly hosts cried out: “Holy! Holy! Holy! Lord God of Sabaoth! Heaven and earth are full of Thy glory!’

(Στώμεν καλώς, στώμεν μετά φοβου Θεού!Άγιος, Άγιος, Άγιος Κύριος Σαβαώθ· πλήρης ο ουρανός και η γη της δόξης σου.)

That was actually: Calling all Angels. The inscription is in Greek: Synaxis ton ennea tagmaton. On the top a triangle and a circle – geometrically representing the Holy Trinity on the rest of the icons all the bodiless powers divided as follows (top to bottom, left to right):

• 1st rank Seraphim, Cherubim, Thrones,
• 2nd, Dominions, Powers, Authorities/ Virtues,
• 3rd rank Principalities, Archangels, and Angels.

The leader of all the angelic hosts is the Archangel Michael. (Bottom row, right in the middle) . 

(For more on the rank of Angels please visit: https://www.oca.org/saints/lives/2013/11/08/103244-synaxis-of-the-archangel-michael-and-the-other-bodiless-powers)

The painting of Sinaxis of the nine orders was inspired icon of the 19th century. It was executed on a special type of gessoed canvas which was cracked and applied with a brownish plant dye that gives to the gold the so called “antique craquelure look”.

For some more theory behind the painting of another icon you may also cvisit: https://angelicon.gr/study-of-christ-pantocrator/