Yannick Nezet-Sequin leads the Philadelphia Orchestra & Philadelphia Singers in a short section of the Mozart Requiem on YouTube.
And here he does a brief promo.
At age 35, Nezet-Seguin has been named Artistic Director designate for the Philadelphia Orchestra. He's also AD for the Rotterdamm Symphony Orchestra since 2007, when he took over from Valery Gergiev.
He studied with Joseph Flummerfelt at Westminster Choir College and started his career as a choral conductor. His own website is here.