The Texas quintet Pentatonix stole America's hearts when they won NBC's a cappella competition The Sing-Off, and their impeccably arranged reworkings of pop standards and modern hits have only increased their fans' fervour, while luring in collaborators like Lindsey Stirling and Dolly Parton. While their vocal harmonies add emotional weight to their covers of A Great Big World's “Say Something” and Leonard Cohen's “Hallelujah”, their precision-grade channelling of musical instruments—the sprightly violin that orbits Clean Bandit's “Rather Be”, the lazy-day trumpet counterpoint of Omi's “Cheerleader”—gives their remakes extra shine.