A symphony is a large orchestral piece, usually in several movements, performed by the full orchestra together, while a concerto features one or more solo instruments backed by the orchestra. If you hear a single piano or violin taking the lead over the orchestra, that is a concerto; if the whole orchestra carries the piece as one, it is a symphony.
The core difference
A symphony is written for the full orchestra, while a concerto is built around a soloist accompanied by the orchestra.
- symphony — a large-scale orchestral piece, usually in several movements: Beethoven's Fifth Symphony is one of the most recognizable pieces of classical music.
- concerto — a piece of orchestral music that features one or more solo instruments: She performed Rachmaninoff's piano concerto with the symphony.
How to tell them apart
Listen for a soloist: a concerto is written to let one performer, often on piano or violin, stand out against the orchestra, with passages that show off their skill. A symphony has no single star instrument; it is a statement for the ensemble as a whole, typically across three or four movements.
The words get mixed up partly because both are large classical forms performed by an orchestra, with the soloist being the clearest signal to listen for when telling them apart.
