Final answer:
Not all 18th-century concertos contained four movements. Concertos from the Classical period typically consisted of three movements.
Step-by-step explanation:
No, not all 18th-century concertos contained four movements.
Concertos from the Classical period typically consisted of three movements: a fast and lively first movement, a slow and expressive second movement, and a lively final movement. This structure was commonly used by composers like Mozart and Haydn.
An example of a famous concerto from the Classical period is Mozart's Piano Concerto No. 21 in C major, which follows the three-movement structure.