Conversation so far:
what is Requiem for Indifferent and Retrospect in regard to Epica?
Requiem for the Indifferent is the fifth studio album by Dutch symphonic metal band Epica.
what songs were on Requiem for the Indifferent?
On 3 February 2012, the band released on iTunes the single Storm the Sorrow“.
what year did requiem for the indifferent come out?
It was released in April 2012
was requiem for the indifferent popular?
General response to Requiem for the Indifferent was positive
how did epica celebrate?
they would celebrate the 10th anniversary of Epica in Eindhoven, Netherlands with a concert called called Retrospect
what happened to the band Epica in 2013?
The band announced on their official website that on March 23, 2013, they would celebrate the 10th anniversary of Epica
is there anything else interesting about Epica's Requiem album?
The concert which would be called Retrospect, would be held in Klokgebouw with a 70-piece orchestra, choirs, international guests and many special effects.

Question: what instruments were in the orchestra?
Self-contained rewrite: what instruments were in the orchestra for Epica's Retrospect concert?