Any music can be considered an "a cappella" arrangement provided it does not contain instrumental notation. The range is huge but the A Capella Challenge is based on what is best defined as contemporary A Capella which focuses on emulating instruments to replicate pop songs. A cappella can be performed with as few as 5 individuals with no defined maximum. Like our Glee Challenge it focuses on contemporary of songs familiar to both singers and audiences.  This encourages a popular and "built in" audience and is no doubt part of its increasing popularity as an art form as seen on TV shows such as pitch battle.

In recent years there have been a number of other developments in contemporary a cappella e.g "beatboxing"  and various post-production technologies which can now be applied to live performance (such as mixing, multi-tracking, looping, effects and pitch modulation).  Such fusions of singing and technology are considered valid a cappella provided the basic input to the process remains the human voice. All of which creates a new unique, educational and innovative music development which is fun to be involved in and fun to watch.