Heart will be networked on weekdays between 1pm to 4pm and 7pm to 6am, and for the whole weekend from Friday 7pm to Monday 6am, excluding 8pm to 12pm. The network consists of three stations in London, the West Midlands and the East Midlands and has a combined weekly reach of 3.3m adults.
Galaxy will be networked on weekdays from 10am to 4pm and 7pm to 6am, and from Friday 7pm to Monday 6am, excluding 8pm to 12pm. The four Galaxy stations in Manchester, Birmingham, Yorkshire and the North East together reach 2.5m adults per week.
The move follows the introduction by Ofcom of new rules governing the amount of local content stations have to broadcast per week.
Ashley Tabor, chief executive of Global, said the changes were intended to cater for advertisers looking for bigger audiences.
"When we started here what you heard on Heart in London was not very similar to what you heard on Heart in the East or West Midlands. They were really quite different radio stations. They were the same name and the same jingles but that's where the similarities ended. It's about offering advertisers a national proposition," he said.
He said that the stations would "be national at the right time of day and local at the right time of day", offering people local programming when they wanted it.
"What you end up with is a quasi-national radio station. People assume networking is about big name DJs. It's not, it's about quality presenters. If you take 50 different radio stations there cannot possibly be 50 good presenters at every station in a particular slot. Why not take the two or three quality class players and put them across the network," he added.
The latter comments may not bode well for the future of the One Network, the 42-station network which Global is acquiring with the rest of GCap Media.