Natural Trumpet

A natural trumpet (often referred to as a Baroque trumpet) is a long, double-folded trumpet without valves. It was the trumpet used across Europe from the 15th through the mid 19th centuries, and is a common ancestor to all modern brass instruments. It is the trumpet that composers like Bach, Handel, Mozart, and Beethoven wrote for, and has had a resurgence in the past 50 years in the performance of Baroque and Classical-era music.

Because it is roughly twice the length of a modern trumpet or bugle pitched in the same key, its harmonic series sits an octave lower, making it possible to play several notes in the middle and lower registers, as well as a complete scale in the upper register.

The natural trumpet only plays the notes of the natural harmonic series. So, as Alison says, modern trumpeters use the tuning holes to flatten the fourth of the scale, to make the sound more tuneful to a modern ear.