Bioshock Infinite Walkthrough Part 57: Flight Of The Songbird (Atrium: Workplace to Security Center)
Head through the empty workspace. Behind the first station you will find a Tear where Pettifog is talking with Elizabeth, who is trying to convince her Booker is never coming. Look near the Tear to find a Locksmith bag if you are lacking any picks. Otherwise head on through to the next part of the workshop.
In the second room of the Workshop is immediately a corridor then the room itself. Inside here, on the far side of the pillar you can hear the Boy Of Silence there. There are a number of Lunatics to deal with if he alerts them, and it is a good idea to get him out of the way. This means fighting. Once again, move to a doorway and do everything you can to keep as much control of the Lunatics as possible. There are not as many as there could have been/were last time so it is easier to deal with.
When the Lunatics have been dealt with, look on the table behind where the Boy of Silence was. Look on the opposite side of the pillar to find a Voxophone: Elizabeth “Debts” and some Salts below it. After that head on out into the Atrium. From there go over to the right and into “Where We Learn”. There is a video you can watch. After that head through the big broken window and down the hallway. Look to the right at the first sign for the Warden's Office. You will find the Kinetoscope “Battleship Falls”. Now head into the next room, the Security Center.
Go into the center of the room and look to the left. You will find a desk with a Gear Box on it. This gives you Rising Bloodlust. This increases Weapon damage for each kill within 10 seconds. A great way to plow through foes if there are a lot of them. Now head over to the right of the desk. You will notice a small, open area with a projector. Approach the projector and look to the right of it. You will find a Medical Kit and a Voxophone: Elizabeth “A Last Chance”. After that find the stairs going up and follow the signs to the Warden's Office.
Once inside the office, grab the Voxophone (Elizabeth “Smothered In The Crib”) on the chair. Be sure to search all the cabinets. They are your last chance to outright collect Salts, Ammo and Health for quite a while. When you are ready, hit the switch in the middle of the console by the bay window. As Booker turns around there is a Boy Of Silence just behind him. After that come 6 Founders. Kill them as effiecently as possible then keep that trend up as you go back toward the elevator.
At the base of the stairs, in the Security Center, you have more Founders to deal with. Kill off the additional 6 in the area and head for the center of the atrium. There you will see the elevator so take it down. Be sure to grab the Voxophone (Elizabeth “Ending It”) inside it. From there just go forward and through the door that was previously closed off.