Complex sentence: In 1873, the first Latvian singing festival was held in Riga, during which most of the songs were Latvian folk songs but one song, composed by Baumaņu Kārlis, later became the national anthem of Latvia.
Split into simpler sentences: In 1873, the first Latvian singing festival was held in Riga, during which most of the songs were Latvian folk songs. Of the new songs performed there, one of them, composed by Baumaņu Kārlis, later became the national anthem of Latvia.