Legendary American jazz musician Charles Lloyd, who headlined the first festival in the Swiss town of Montreux in 1967, kicked off the two-week celebration of music alongside fabled jazz pianist Monty Alexander, who first played Montreux in 1976.
"It's very emotional, because those two guys are part of the history of the music and to have those two guys loving Montreux, helping us celebrating the 50th, it is certainly one of the most beautiful gifts that I could expect," festival chief Mathieu Jaton told AFP ahead of the concerts, as all around him staff rushed to make the final preparations for the annual influx of music lovers.
Earlier on Thursday, with the sun glimmering on nearby Lake Geneva, Alexander and his band gathered for a sound check in the dark interior of Montreux's old Casino, the festival's original home and around a kilometre from the current main concert venues.
With a broad smile, the Jamaican-born musician sat down at his grand piano and let his fingers fly.
"I will be bringing it. Not just the straight ahead so-called classic version, but I'm going to bring in some, as we say in Jamaica, yard roots rhythm and get people to groove too," the 72-year-old told AFP.
Lloyd, 78, who primarily plays tenor saxophone and flute, also said he was looking forward to Thursday's concert.
"I'm doing this because I love it, and it gives me something, and it is about inspiration and consolation, and the world we live in I feel could use that, so I want to share that with others," he told AFP.
While the opening night was all about jazz, the Montreux festival long ago drastically expanded it repertoire, becoming a magnet for prominent names and rising stars across music genres.
This year's main attraction is perhaps folk rock icon Neil Young. The Canadian singer-songwriter will hit the main stage on July 12th, 15 years after his only previous appearance at the festival.
He will be joined by a seemingly endless list of stars, including British experimental rocker PJ Harvey and US punk legend Patti Smith.
The 2016 edition will also feature US rock band ZZ Top, with their recognisable long beards, and Northern Irish singer-songwriter Van Morrison, US singer-songwriter Lana Del Rey and archetypal guitar hero Carlos Santana.
Also included in the line-up is legendary American producer and composer Quincy Jones, considered one of the greatest supporters of the festival, as well as British soul and pop band Simply Red.
British rock band Muse will be there too, playing "in a little hall of 4,000 capacity, which is just amazing," Jaton said.
Also on the ticket is influential English hard rock band Deep Purple, who have a deep connection with Montreux.
The band's iconic "Smoke on the Water" tells the story of a fire that took place during a Frank Zappa concert here in 1971.
Festival founder Claude Nobs, who died in 2013, rescued a number of people from the flames and was immortalised in the song as "Funky Claude".
"Every night is a headline," Jaton insisted. "I could name all of them because to me all of them are stars."
Jaton, who worked closely with Nobs for two decades, hailed his "crazy idea" that half a century on has morphed into "a brand travelling all over the world."
"I'm so proud to be part of it, so honoured and so happy every day to wake up and say: I'm running one of the most amazing events in the world."