If you've never heard the a cappella group Pentatonix sing, you are missing out! A cappella is when individuals or groups perform songs using only their voices. Pentatonix has revitalized this difficult art in recent years, making it extremely popular around the world. The five part group includes lead singers Kirstin Maldanado, Mitch Grassi, Scott Hoying, and the beatboxing-bass duo of Kevin Olusola and Avi Kaplan. After winning the national television show The Sing Off, the group has released multiple albums of holiday and cover songs. Wanting to branch out from cover songs, they recently released their first original album in October of 2015. If you've become a true Pentaholic in the last few years, here are a few groups similar to Pentatonix to discover.

1. Home Free

Home Free is another five-part a cappella group, but they sing country! They're very revolutionary in the a cappella world because almost nobody has focused on country a cappella music. The group won the fourth season of The Sing Off on NBC and have made a name for themselves by touring all over the country. Here's them taking on Zac Brown Band in a solid performance from when they were on The Sing Off. (performance starts at 1:35)

2. Todrick Hall

While not an a cappella singer, Todrick Hall has some pretty awesome YouTube videos of himself singing...with himself! He creates mashups of songs by one artist, such as Beyoncé or Taylor Swift, and then sings all four parts of it. He also collaborated back in 2013 with Pentatonix on "The Wizard of Ahhhs", the story The Wizard of Oz told through modern day music. Check it out for yourself below.

3. Dartmouth Aires

This group from Dartmouth College was so good they fell second only to Pentatonix themselves in Season 3 of The Sing Off. Unfortunately, they tapered off after competing on the Sing Off, but every single one of their performances was spot on. The group consisted of many versatile singers with some wacky personalities. Their Queen medley with songs like Killer Queen and Bohemian Rhapsody, has hundreds of thousands of views on YouTube and is absolutely genius.

4. Straight No Chaser

Straight No Chaser is an a cappella group that formed in the 90's and has climbed their way up to touring, performing, and releasing albums in the past few years. Straight No Chaser's style tends to drift to older songs such as Madonna's Like a Prayer, while also incorporating today's popular music such as Jason Mraz's I'm Yours. They are the masters of mashups, as you can see in this genius combination of Billie Jean and Poison.

5. Triptyq

Last, not least, and possibly my favorite group on this list, we have Triptyq. Strange name, awesome music. Triptyq is a group consisting of singer Antoniette Costa, classical pianist Tara Kamangar, and the one and only, Kevin K.O. Olusola from Pentatonix. The trio only recently started collaborating, but just released their phenomenal album titled "The Triptyq Sessions". Kevin Olusola's simultaneous beatboxing and cello playing will immediately make you wonder if he's human. My favorite song by Triptyq is a spy-esque song you might find in an undercover spy movie, called Camouflage Me.

If you liked Pentatonix already, you'll love each of these groups. Have fun discovering!