Styling A Great Big World's Say Something as a soft, slow piano ballad makes it a fairly unlikely single in this era of over-auto-tuned, over-synthesized dance-pop anthems — and, perhaps not surprisingly, the song exploded on the charts only after Christina Aguilera re-recorded a version with the New York duo. Pentatonix's version aside, it's as unlikely an a cappella cover as it is a pop single, but the YellowJackets do a beautiful job with this song, turning the initial piano intro into the sound of chiming bells and adding a crescendoing hum to give the song an even more regal intro.

And then, there's a surprise: the lyrics aren't those from Say Something. This is a re-imagined cover of the Postal Service's Such Great Heights, twisted from its electropop roots into a tender piano ballad. It's beautiful and dramatic, and soloist Joshua Huang does a masterful job of delivering the lyrics at a tempered, unhurried pace, as the YellowJackets chime in with Say Something lyrics in the background.

There's another twist to the arrangement later: as Huang and the group switch places, he takes over the Say Something lead while they carry on with Such Great Heights. It's handled seamlessly and without fanfare, melding the messages of the songs without drawing attention to the switch.

This arrangement is beautiful, and the YellowJackets perform it beautifully. This is the type of creativity that many groups strive for, and the YellowJackets have delivered it here effortlessly. Say Something is proof that groups don't need flashy studio effects and up-tempo songs to deliver a stunning performance.