Instruments produced during the Baroque period had no finger/vent holes in them to aid intonation and note production (other than a few cases which use the same principle but for a different purpose). They were limited to playing notes from the harmonic series, and were popular for many years before the advent of Equal Temperament. Instruments without vent holes are commonly referred to as “Natural Trumpets”
To modern ears Natural Trumpets can sound “out of tune” as some of the harmonics do not fit in with equal temperament. During the 20th century two vent systems were developed to bring these trumpets closer to equal temperament. Using vent holes flattens the sharp 11th harmonic to a natural f in the key of the trumpet and raises the flat 13th, giving a more equal scale. Our trumpets come with either the four hole vent system developed by Michael Laird, no vents at all, or one vent.
The one vent instrument is a compromise between using a Natural Trumpet and a Baroque instrument. When using vents to produce notes the character of the sound is slightly different than when playing without holes. The trumpet with just one hole – used only to make the 11th and 13th harmonics sound “in tune” – has a more even tone quality throughout it’s range.