A symphony orchestra is composed of 4 categories of instruments:
Strings : Violins I, Violins II, Violas, Cellos and Double basses;
The woodwinds: Flutes, Oboes, Clarinets and Bassoons;
Brass: Horns, Trumpets, Trombones and Tuba;
Percussions
In 2024-2025, the OSJM have 77 musicians : 45 strings, 13 woodwinds, 14 brass and 5 percussions.