In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

What are a capella singers known to do with their voices?, Context: In addition to singing words, some a cappella singers also emulate instrumentation by reproducing instrumental sounds with their vocal cords and mouth. One of the earliest 20th century practitioners of this method were The Mills Brothers whose early recordings of the 1930s clearly stated on the label that all instrumentation was done vocally. More recently, "Twilight Zone" by 2 Unlimited was sung a cappella to the instrumentation on the comedy television series Tompkins Square. Another famous example of emulating instrumentation instead of singing the words is the theme song for The New Addams Family series on Fox Family Channel (now ABC Family). Groups such as Vocal Sampling and Undivided emulate Latin rhythms a cappella. In the 1960s, the Swingle Singers used their voices to emulate musical instruments to Baroque and Classical music. Vocal artist Bobby McFerrin is famous for his instrumental emulation. A cappella group Naturally Seven recreates entire songs using vocal tones for every instrument.
In addition to singing words, some a cappella singers also emulate instrumentation by reproducing instrumental sounds with their vocal cords and mouth