SAO PAULO (Reuters) -Brazilian singer Gal Costa, one of the most distinctive voices from the country’s Tropicalia movement, has died at the age of 77. “It is with deep sadness and a heavy heart that we communicate the death of singer Gal Costa,” said her official Twitter account. “We appreciate everyone’s love at this difficult time.” Tributes poured in from many of Brazil’s biggest names in politics and entertainment. President-elect Luiz Inacio Lula da Silva said Costa was “one of the greatest singers in the world.” “Her talent, technique and daring enriched and renewed our culture, shaped a…