The contrabassoon, bass clarinet, piccolo, xylophone, harp, accordion and arpeggione were introduced during the Romantic era. These instruments allowed composers to capture the emotions that they wanted to express in their music.
The Romantic period saw the introduction of new instruments that came to define the era. The arpeggione, a guitar-shaped 6-string cello that is played with a bow, was invented in 1823 and was regularly used in many Romantic era musical pieces. Other instruments, such as the bass tuba, saxophone and trumpet with three valves, were created and popularized during the Romantic era.
Some instruments, including bells, triangles and celestas, became more common during the Romantic era because they helped create colorful musical landscapes. Many of these instruments were around for centuries, but were not regularly used because they did not meet the structural standards that were established in the Classical era of music. Composers of the Romantic era found these standards to be far too rigid, which is why so many of them chose to introduce new instruments.
A Romantic era piece that best captures the use of these instruments is Tchaikovsky's "The Nutcracker," which combined the sounds of a celesta and bass clarinet to create an eerie setting in the ballet's famous "Dance of the Sugar Plum Fairy."