From the melodic and harmonic point of view, forró makes heavy use of the escala nordestina (literally North-eastern scale), which could be characterised as being a mixture of the Lydian and Mixo-lydian modes. The North-eastern scale represents the basis of a large part of the more traditional forró and the forró pé-de-serra, similar to the way the blues scale is the basis for the music of the Mississippi Delta. The escala nordestina is most evident in pieces such as "Vem Morena", baião of Luiz Gonzaga. The accordion is the typical melody instrument used in forró, and is sometimes called the "Soul of Forró" or the "Soul of the Sertão", referring the region where Forró has originated.