According to Easton's Bible Dictionary, trumpets in the Bible were of a great variety of forms and were made of various materials. Some were made of silver (Num. 10:2), and were used only by the priests, announcing the approach of festivals and in giving signals of war. Some were also made of rams' horns (Josh. 6:8). These were blown at special festivals and to herald the arrival of special seasons (Lev. 23:24; 25:9; 1 Chr. 15:24; 2 Chr. 29:27; Ps. 81:3; 98:6). This type of trumpet, the shofar is still blown today in Jewish services on Rosh Hashanah (the Jewish New Year) and Yom Kippur.
"Trumpets" are among the symbols used in the Book of Revelation (Rev. 1:10; 8:2). (See Horn.)
Books
Tarr, Edward (1988). The Trumpet. Amadeus Press. ISBN 0931340136.
International Trumpet Guild (http://www.trumpetguild.org/) - a trumpet players' group with many online resources including a frequently-updated diary, links hub, jobs etc.
was founded in 1974 to promote communications among trumpet players around the world and to improve the artistic level of performance, teaching, and literature associated with the trumpet.
Links to trumpet related websites, materials, repertoire, and pedagogy provide quick access to nearly any facet of trumpet and trumpet related information.
The International Trumpet Guild is in the process of transitioning membership processing and accounting practices in order to improve service to its members.
Another relative of the trumpet is the flugelhorn, sometimes dubbed the "valvedbugle".
The length to add for the three valve intervals is calculated by using the fact that the frequency of an air column is inversely proportional to length.