Final answer:
The larger group performing a concerto is best described as an 'orchestra'. Singular or plural pronouns and verbs can be used depending on whether the group acts as a single unit or individuals.
Step-by-step explanation:
The term that best describes the larger group performing a concerto is orchestra. In a concerto, the orchestra and a soloist interact, with the orchestra providing the accompaniment while the soloist showcases their virtuosity. As per collective nouns agreement, when referring to the orchestra acting as a cohesive whole, it is appropriate to use a singular pronoun and verb form, such as 'The orchestra performs its repertoire regularly.'
However, if the individual members are the focus, a plural form can be used: 'The orchestra members tune their instruments before a concert.'