Complex sentence: Verdi had been giving singing and piano lessons to Margherita and they spent time playing and talking about music, but by 1830, Margherita's mother discovered that the young couple were in love.
Split into simpler sentences: Verdi had been giving singing and piano lessons to Margherita and they spent time together playing and talking about music. But by 1830, Margherita's mother discovered that the young couple were in love.