Contemporary a cappella includes many vocal groups and bands who add vocal percussion or beatboxing to create a pop/rock/gospel sound, in some cases very similar to bands with instruments. Examples of such professional groups include Straight No Chaser, Pentatonix, The House Jacks, Rockapella, Mosaic, and M-pact. There also remains a strong a cappella presence within Christian music, as some denominations purposefully do not use instruments during worship. Examples of such groups are Take 6, Glad and Acappella. Arrangements of popular music for small a cappella ensembles typically include one voice singing the lead melody, one singing a rhythmic bass line, and the remaining voices contributing chordal or polyphonic accompaniment.