Contemporary a cappella is fairly distinct from your typical mainstream categories, and even within this style, there's even more room for diversity.
A subcategory of contemporary a cappella that is currently seeing immense growth is South Asian music. Groups such as Penn Masala have seen tremendous success both within and outside of the a cappella realm. Other groups are also beginning to make a name for themselves and pull away from the pack. St. Louis University's Astha is one such group who is making a name for themselves through inventive arrangements.
In the group's fusion of Lorde's "A World Alone" and Arijit Singh's "Sooraj Dooba" they are excelling in the art form of mashups. Seamless hand-offs of the solo along with careful balancing of overall parts makes the song sound refreshing and unconventional....things we can't get enough of in a cappella.