After reports earlier this week that North Korea tested what its government claims was a hydrogen bomb, South Korea has responded with an old wartime tactic: using giant loud speakers to blast anti-government propaganda across the DMZ (demilitarized zone) that marks the border between the two countries.

This time, the Sydney Morning Herald reports, they've added K-pop to the propaganda routine, featuring a girl group called Apink, South Korean folk musician Lee Ae Ran, and boy band Big Bang:

South Korea started blasting the music and messages Friday morning, according to Agence France Presse, and on what also happens to be Kim Jong-Un's 33rd birthday.

The speakers have been in place since the Korean War of 1950‚Äď53, but this is just the second time they've been used since then. The tactic is aimed at breaking down the North Korea regime's tight control on information and culture in the country. The first was in August last year, and escalated into artillery fire between the nations.¬†Deutsche Welle reports that part of the agreement they made was that South Korea would not use the speakers again "unless an abnormal case occurs."

Though it seems doubtful that what North Korea tested was actually a full-scale hydrogen bomb, the international response has been widespread condemnation from the U.S., Japan, and the United Nations Security Council. Whether South Korea will take action beyond the broadcasts, like increasing sanctions or military presence along the border, remains unclear.