So what exactly are mandolin orchestras?
Mandolin orchestras include mandolin players in two sections usually (Firsts and Seconds - the First section mandolin players usually play mostly melody lines while the Second mandolin player often have a more difficult role of playing contrapunctal lines and off beat parts and don't get the melody quite as often), mandola players (mandolas are larger instruments with longer strings and are pitched lower - usually an octave lower - than mandolins, mandocello players - mandocellos are much bigger with much longer strings and therefore lower in pitch than mandolas by a fifth, classical guitar players and double bass or acoustic bass guitar players.
The variety of instruments provide a wide range of pitches and textures to the sound of the mandolin orchestra.
There is a large repertoire of music composed specifically for Mandolin orchestras as well as many arrangements of music originally composed for full symphony orchestras and other genres of ensemble.
Mandolin orchestras were an extremely popular format of ensemble in Europe, America and Japan but their numbers have waned as popularity of the mandolin as a classical instrument declined in the last century.