Langford says: "Moving to BIG Concerts is an opportunity that I simply could not resist - the live music arena is a natural step into a dynamic entrepreneurial environment.
"I know that I leave 5FM at time when it is in its best health ever; the ship has been turned around and having achieved what I set out to do, it is time to face new challenges."
Listenership now sits at 1.3 million listeners a week and black listeners make up more than 50% of the audience.
Big Concerts Managing Director Attie van Wyk says: "We have achieved record-breaking sales in the first quarter of this year and a nomination as Pollstar Magazine's International Promoter of The Year. John's knowledge, experience and fresh insights will no doubt make him an asset to the company, and I am confident that with John joining the team, BIG Concerts will keep growing from strength to strength."