Given the task definition and input, reply with output. In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Engelbert Humperdinck has been a major contributor to the sound of what musical genre?, Context: Artists contributing to this format include mainly soft rock/pop singers such as, Andy Williams, Johnny Mathis, Nana Mouskouri, Celine Dion, Julio Iglesias, Frank Sinatra, Barry Manilow, Engelbert Humperdinck, and Marc Anthony.
pop