My absolutely most favorite singing music group, The King's Singers, have just won a Grammy for their CD "Simple Gifts" (www.signumrecords.com) Classical Crossover group. You must hear them.
I have been following them since 1983 and have every CD or tape they ever produced. They are the most brilliant a cappella singers around today.
Do go to You Tube and hear them. The best pieces there are "Blackbird", "Danny Boy" and if you want some fun, try "The Barber of Seville Overture". You won't be disappointed.
Link to You Tube here:
These are the Songs on this Grammy Award winning CD (Sorry you have to squint):