Police have launch an investigation to see if rules were flouted by organisers.
It is not clear what triggered the stampede at the service.
The victims include three girls and two boys aged between 14 and 16 and a 39-year-old woman who accompanied her daughter to the concert.
Local hospital officials confirmed the fatality as thousands of fans rushed to enter the Stade Municipal de Mahamasina in the country’s capital ahead of the eagerly-awaited fixture.
The stampede happened when a sudden rush among mourners arriving at the site caused many to lose their balance and fall.
The deaths occurred after a brawl broke out during a middle school graduation party and someone detonated the tear gas.
Studies by the United Nations and other groups have warned that the country's water crisis will worsen unless action is taken.
TV footage showed commuters trying to revive the injured by pumping their chests and also carrying some down stairs to street level.