Baroque pop
Baroque pop is a rock music subgenre that mixes both rock and classical music. It was created by musicians in the 1960s by adding classical instruments like harpsichord, French horns, oboes, and string sections. It became popular with both teenagers and adults at the time. Examples can be found on The Beach Boys' Pet Sounds and recordings made by Phil Spector.  It is also referred to as chamber pop, among other names.