Mon Rivera (1924-1978) was born Efraín Rivera Castillo in Mayagüez, Puerto Rico to Ramon Rivera Alers, from whom he inherited the nickname “Mon.” Ramon, now known as “El Viejo Mon Rivera,” was living in extreme poverty in the 1930s. He made a living advertising shops on the streets through songs (kind of like a commercial jingle in real-time). He was extremely adept at improvising lyrics and rhythms to portray the everyday life of people in Mayagaüez. He was, in a sense, the town troubadour. Accompanied by a tambourine, he would sing plenas that his son Efraín would later make famous, such as “Alo! Quien Ñama?” and “El Gallo Espuelérico,” which were recorded with Moncho Leña’s orchestra in New York City in the early 50s.

Mon Rivera inherited the gift of music from his father, but he was also extremely adept at baseball. He was the shortstop for the Indios de Mayagüez, who he played with from 1943-1945. He holds the league record for most triples in a game and most consecutive doubles in a double-header.

He began to perform Mexican folk songs as part of “El Dúo Huasteco” with Germán Vélez. They caught the attention of concert promoter Gilbert Mamery, who featured them in his shows as the San José Theater in Mayagüez. Mon then joined the orchestras of local bandleaders, such as Moncho Leña and William Manzano, as a vocalist and percussionist. He moved to New York City with Moncho Leña’s orchestra in 1953, where they filled in for Tito Puente, Tito Rodriguez, and Machito at the Palladium while they were on tour.

In New York City, Mon was extremely active, lending his vocal chops to several groups including those of Luis Quintero and Jose Cotto.

He is nicknamed “Rey del Trabalenguas” (“King of the Tongue Twisters”) for his agility with words, as exemplified in the hit “Karacatis-Ki,” and “A Papa Cuando Venga”.

Mon Rivera’s orchestra is known as a trombanga (a trombone ensemble), which would become a distinguishing aspect of salsa brass sections such as those of Willie Colón and Eddie Palmieri.