Conversation so far:
Where does the Vienna Boys Choir perform?
CANNOTANSWER.
How large is the Vienna Boys Choir?
The choir has for the first time had to advertise for recruits.
Were they able to get enough recruits to keep going?
The Vienna Boys' Choir has sought to update its image.
How have they changed their image?
recording pop music selections and adopting an alternative uniform to the sailor suits used since the 1920s.

Question: What is their uniform now?
Self-contained rewrite: What is the Vienna Boys' Choir uniform now?