This is the 3185th most frequent Russian word.
музыкальный
Musical.
Here, 'музыкальная' is an adjective describing the noun 'школа' (school), indicating its specialization in music.
У нас в районе есть музыкальная школа.
In our neighborhood, there is a music school.
In this instance, 'музыкальном' is the instrumental case of the adjective 'музыкальный', modifying 'инструменте' (instrument).
Я мечтаю научиться играть на музыкальном инструменте.
I dream of learning to play a musical instrument.
Here, 'музыкальный' again serves as an adjective qualifying 'спектакль' (performance), emphasizing its musical theme.