Composers like Bach's work might be referred to as "classical music"" since his music in the Baroque style.
Form is a very important to any classical composer particularly on the instrumental music forms. The symphony, the concerto, and the sonata forms, which matured in the Classical period, replaced the most common instrumental music forms of the Baroque such as the toccata, fugue, and concerto grosso. When it comes to Classical music, the standard symphony has four movements; the inner two usually include slow movement based on dance form. There are other popular choices for the outer two movements, but the sonata form is the most common.
Classical composers continued to use the same chords, harmonic progressions and cadences that were used by Baroque composers especially the rules of harmony that have governed Western music for centuries set up in the Baroque period. However, they changed the chords less often and used less chromaticism. When they had to change keys in a music piece, it was a clear modulation using a standard chord progression.
In the Romantic era, composers did not reject Classical composition techniques just the way Classical rejected the Baroque, but they instead explored and developed them. Western Popular music is using the same "vocabulary " of scales and chords as Classical music constructing melodies and chord progression using them in very similar ways, has spread in popularity throughout the world, both on its own and hybrid styles such as jazz and world music. The close explanation of classical era is generally defined by when the modern sonata form became from the rounded two-part form of the Baroque period. In this era, there was a development of the trio sonata emerging into the string quartet; concerto grosso into symphony concertante; and the occurrence of symphony and a new solo concerto when they both expanded that each movement became independent in a small self-sufficient unit.