He founded his first conjunto in Havana in 1957. In the 1950s, Alonso sang with Benny Moré and Fernando Álvarez, a trio popularly known as  "The Three Musketeers".
Alonso established his first ensemble in Havana in 1957. Throughout the 1950s, he performed with Benny Moré and Fernando Álvarez, who were collectively known as "The Three Musketeers."