José Rodríguez Alvira
When reading music written for a transposing instrument we must not forget that the notes produced by the instrument are not the same notes as those written. We must know the transposing interval to be able to know the real note that will be heard. Let's take a trumpet in Bb as an example. In the previous table we saw that the transposing interval for the trumpet in Bb is a descending major second. This means that any note played by the trumpet will sound a major second lower. If a trumpet player plays a melody in C major we would hear it a major second lower in the key of Bb.
For example, the following melody played by a trumpet in Bb:
will sound like this:
If played by a horn in F that sounds a perfect fifth lower we would hear the melody a perfect fifth lower: