Background: The Ink Spots were an American pop vocal group who gained international fame in the 1930s and 1940s. Their unique musical style led to the rhythm and blues and rock and roll musical genres, and the subgenre doo-wop. The Ink Spots were widely accepted in both the white and black communities, largely due to the ballad style introduced to the group by lead singer Bill Kenny. In 1989, the Ink Spots (Bill Kenny, Deek Watson, Charlie Fuqua and Hoppy Jones) were inducted into the Rock and Roll Hall of Fame, and in 1999 they were inducted into the Vocal Group Hall of Fame.
Context: In 1936, Jerry Daniels was replaced by a 21-year-old singer from Baltimore, Bill Kenny, who signed on with the Ink Spots after winning first place in an amateur contest at Harlem's Savoy Ballroom. Three years later, Kenny was credited for bringing the group to global success with his unusual high tenor ballad singing. In 1938, after being in the group for two years, Bill Kenny started to introduce the group to a new format that he called "Top & Bottom". This format was used primarily for ballads rather than the uptempo "jive" songs the group was used to performing. This format called for the tenor (Bill Kenny or Deek Watson) to sing the lead for one chorus followed by a chorus performed by bass singer Hoppy Jones reciting the lyrics rather than singing them. After a chorus of the "talking bass" the lead tenor sang the rest of the song until the end. The earliest example of their "Top & Bottom" format is from a radio broadcast from 1938. The song entitled "Tune In on My Heart" features Bill Kenny taking the lead and Hoppy Jones performing the talking bass. The year 1938 also saw Bill Kenny taking his first feature solo in Decca studios. His feature was on a song entitled "I Wish You the Best of Everything". Although it wasn't in the "Top & Bottom" format it was a ballad and used the signature Ink Spots guitar intro. Even though it got a good response, it wasn't very successful in terms of record sales and didn't reach the pop charts.
Question: What was Top and Bottom ?

Answer:
This format called for the tenor (Bill Kenny or Deek Watson) to sing the lead for one chorus