What is a sackbut?
A sackbut is nothing more than an early trombone! The term "sackbut" likely came from the French saqueboute, meaning to pull ("saquier") and thrust, or push ("buter"). This word also referred to a lance-like weapon used in the French military, armed with an iron crook, which could pull an enemy off his horse. Today, the word "sackbut" is used merely to distinguish the early trombone from its larger, louder grandchildren.
That all said, there are a lot of differences between a modern trombone and a sackbut! First, the sackbut is smaller, with thinner metal and a conical bell. The function of a sackbut was also very different from the function of a modern trombone. Sackbut players had to blend easily with voices, and their music was often written in a "colla parte" style, meaning that they played along with choral lines or even replaced singers in church choirs. You could also find a sackbut player in a town band, playing with shawms, dulcians, and other "loud" instruments.
As music composition changed, and composers such as Beethoven began to use the trombone harmonically and symbolically, the trombone's size and weight had to adapt to these new conditions. Symphony orchestras grew in size, and a heavier instrument with a more flared, trumpet-like bell could better cut through a huge group of musicians and be heard at the back of a concert hall. As a result, the modern trombone bell is about three times the size of a sackbut bell!
The sackbut mouthpiece has a flat, sharp rim. This shape is important for articulation and correct tone production on the instrument. A sackbut player's goal is to sound as close to the human voice as possible!