Singer was chief financial officer and a director on the main board of GMG since 2011.
He replaces Michael Connole, who has joined Quarto, the book publisher and distributor.
Singer was previously chief financial officer EMEA at WPP’s media buying unit GroupM, where he had responsibility for about 8,000 staff across 30 countries.
Prior to joining GroupM, he held a number of senior roles at BSkyB, including director of group finance and head of finance for Sky Networks, Sky Media and Sky Sports. He has also worked as an analyst at the BBC.
Singer said: "It’s an incredible time to join Global. Over the past few years, I’ve watched the company as it has stimulated the commercial radio sector’s return to growth, and more recently as it has grown its interests in the music and entertainment world in the UK and the US.
"I’m looking forward to joining the leadership team and playing a role in the next stage of the Global journey."
In his new role Singer will report into Global’s group chief executive, Stephen Miron.
Miron said: "Darren brings to Global exceptional leadership, knowledge and experience, having worked at some of the world’s most prestigious media and entertainment companies.
"We’re delighted to welcome Darren to Global where he will be a tremendous asset as we continue to fulfil our ambitious plans for the business."