This is what the Vindictive Soliloquy masterpiece does:
Your bombastic speech creates booming reverberations of sound.
Prerequisite(s): Perform (act), Perform (oratory), or Perform (sing) 10 ranks.
Cost: Feat or 4th-level bard spell known.
Effect: You provide an impassioned monologue from the point of view of a noble queen, voicing her inner turmoil at being betrayed by her own sister and calling for justice to strike from the heavens. If you perform this masterpiece with the Perform (sing) skill, it is a tempestuous aria instead of a rousing soliloquy.
Upon completing the performance, you may conjure bolts of lightning as though you had cast call lightning storm, except the bolts are made of elemental thunder and deal sonic damage rather than electricity damage. The bolts do not increase in damage if outdoors in a stormy area. Instead, in any environment, you may attempt a DC 25 Perform check as part of the standard action to call a bolt.
If your Perform check is successful, that bolt deals 5d10 points of sonic damage instead of 5d6.
Use: 5 bardic performance rounds.
Action: 5 full rounds.
Now the way I read it, it's saying that you can do the damage while you are performing, but someone else could easily see this as only coming into effect after the 5 full rounds are complete.
So this masterpiece is either a decent alternative for a 4th level spell for bard, or completely useless as it would simply take too long.
Which one is the correct interpretation?