Juan Gabriel performs at The Forum at The Forum on Aug. 26, 2016 in Inglewood, Calif.

Juan Gabriel performs at The Forum at The Forum on Aug. 26, 2016 in Inglewood, Calif. 

Gabriel Olsen/Getty Images

When Juan Gabriel died from a heart attack on Aug. 28, the Mexican singer-songwriter was enjoying a level of commercial success rare for an artist in the prime of his career, let alone a 66-year-old legend.

His last thee studio albums debuted at No. 1 on Billboard's Top Latin Albums chart, with his 2015 release Los Duo moving 138,000 units and becoming the top-selling Latin album of 2015, according to Nielsen Music. An active live performer, he had notched the highest-grossing U.S. Latin tour of 2015 -- close to $40 million, ­according to Billboard Boxscore, plus nearly $10 million more from 12 dates at Mexico City's Auditorio Nacional alone -- all of which brought him to No. 18 on Billboard's 2015 Money Makers list. At the time of his death, Gabriel had just launched a 30-city U.S. tour; he performed at The Forum in Inglewood, Calif., on Aug. 26, the night before he suffered a fatal heart attack as he prepared to fly to El Paso, Texas, for the next show.

Yet those numbers only scratch the ­surface of his worth.

Dogged by poor business deals with previous managers and by tax problems in both the United States and Mexico, Gabriel saw his career stabilize after ­signing a global agreement with Universal in 2008 that included recordings and ­publishing. According to sources close to the negotiations, Gabriel's advance for the publishing alone approached $7 million and was recouped in less than five years. In 2010, Ivan Aguilera, the oldest of his five children, took over as his manager. (Aguilera has said publicly that his father had established how his inheritance would be divided, but had not provided more details at press time.) This allowed Gabriel to focus on his music. "The artist knows how to sing, not how to count," Gabriel said in a 2002 interview with Univision.

Beyond the Los Duo album and its 2016 follow-up, Gabriel released two other albums on Universal in the past two years, including Vestido de Etiqueta, which debuted at No. 1 on the Top Latin Albums chart in August. Those albums ­combined have sold 2 million copies globally, ­according to Universal; he also produced albums for other artists (La India and Isabel Pantoja) covering his songs.

Juan Gabriel Sales & Streams Soar Following His Death

In terms of audio and video streams during the last two years, Gabriel has accumulated 485 million and 326 million, respectively, according to Universal, of which just 14 percent and 8 percent have come from the United States. While his total U.S. album sales stand at 3.4 ­million, that number does not include sales from the nontraditional retail outlets that ­dominated the U.S. Latin-music market until around a decade ago.

Publishers tell Billboard that the ­numerous covers of Gabriel's songs make it difficult to estimate the value of his catalog. Yadira Moreno, managing director of Universal Music Publishing Mexico, which administers the entirety of Gabriel's ­catalog, says, "He is one of the top five Latin-American composers [in history], because of the capacity that his work has to be exported and adapted into other ­languages -- that's not common. This is a very active, very lucrative writer."

Juan Gabriel Tribute

Of Gabriel's 660 registered ­compositions with Universal, 23 have been adapted to other languages -- including Japanese and Afrikaans -- with his 1971 hit "No Tengo Dinero" adapted to five languages. Through the years artists ranging from Marc Anthony to Maná to Luis Miguel have scored hits with his songs.

And while the singer had long been ­reticent to license his music for ­advertising, in recent years he opened the door, ­including a 2015 campaign for Mexican juice brand Jumex that used a cover of his song "Buenos Días Señor Sol." Most recently, he had a big synch payday with music used in Hasta Que Te Conocí, the TV series based on his life that aired earlier this year on TV Azteca in Mexico, and will begin airing stateside on Telemundo on Sept. 11. Gabriel also received a fee for the rights to his life story, the script and ­production for which he approved.

Juan Gabriel Mourned in Mexico City

Added up, the value of Gabriel’s music assets at the time of his death was an estimated $45 million.

"With all due respect to other big stars," says Jesus Lopez, chairman/CEO of Universal Music Latin America & Iberian Peninsula, "he has been the biggest Latin artist of the past 40 years -- in all aspects."

This article was originally published in the Sept. 17 issue of Billboard.