This three-part documentary series sees the Grammy-award winning jazz and soul star examining how singing has changed over the past century. He covers a vast range of performers, beginning with arguably the first pop star on the planet, the Italian tenor Enrico Caruso. He then moves onto some of his favourite performers such as Ella Fitzgerald, Mahalia Jackson, Freddie Mercury, Prince, Whitney Huston and Mariah Carey. Interviewed as part of this documentary are Adam Lambert, Dave Grohl and Beck. Gregory Porter\u2019s Popular Voices is on BBC Four at 22.00.