~のを => Nominalize verbs N5
Nominalization
祭 (に) => when; at the time of; in the case of ~ N2
Time
に先立って => before; prior to ~ N2
に[先立「さきだ」]って/に[先立「さきだ」]ち/に[先立「さきだ」]つ => Before A occurs/takes place N2
Time, Situation
...を...みる => judging from; seeing that ~ N4
Deduce
...を...にする => to make something ~ N4
Purpose, target
姿を見せる => figure; appearance N3
Ability
…ばあいをのぞいて => Except for N2
Exception
ものを => Although A, (unfortunate result) B N1
Contrast/Surprise
...が...を...みせる => make it look like... N4
Base, base
を…とする => is considered, is regarded as N2
Consider it
~ものを      => But, Although, If only, I wish I had N1