How does the Bb trumpet's sound compare to concert pitch?

The Bb trumpet is classified as a transposing instrument, meaning that the pitch it sounds differs from the written pitch in sheet music. When a Bb trumpet plays a written C, it sounds a Bb. This means that the trumpet produces a sound that is a major second lower than concert pitch. As a result, when performing with concert pitch instruments, such as a piano or concert flute, the trumpeter must read music that is a whole step higher than the intended sound they want to produce.

For example, if a composer writes a score for a Bb trumpet in the key of C, the pitch that is actually heard is Bb, which is one step down (or a major second lower) from that written pitch. This characteristic of the Bb trumpet is essential for performers and composers to understand to ensure accurate pitch during ensembles and solos.