Prior to the arrival of the Spanish, indigenous music was played with rattles, drums, flutes, and conch-shell horns as part of religious celebrations. The Spanish introduced violins, guitars, harps, brass instruments, and woodwinds, which mostly replaced the native instruments. The Europeans introduced their instruments to use during Mass, but they were quickly adapted to secular events. Indigenous and mestizo peoples learned to play and make these instruments, often giving them modified shapes and tunings. In addition to instruments, the Spanish introduced the concept of musical groups—which, in the colonial period, generally consisted of two violins, a harp, and various guitars. This grouping gave rise to a number of folk musical styles in Mexico.