Mexican Mariachi Bands in London for Hire – Mariachi can refer to the music, the band or just one musician. Most Mariachi Bands in London consist of a vihuela, a high-pitched, round-backed guitar which provides rhythm, a bass guitar called a guitarrón which also provides rhythm and a Trumpet, According or Violin as the lead instrument. There is generally no lead singer as in other kinds of group with all players singing choruses and taking turns singing the lead.