About five years ago, I was working on the staff of a summer youth band. The other band directors I worked with there are great teachers and good friends to this day. That summer, one of the trumpet players on staff introduced me to a practice tool that has become a must-have item for the majority of my students. 
The B.E.R.P., which is short for Buzz Extension and Resistance Piece, is a plastic device which attaches to the lead pipe of any major brass instrument. The instrument's mouthpiece can be inserted into the instrument as usual, or it can be inserted into the BERP as seen in the picture to the left. There are small openings at the base of the BERP chamber that allow air to escape. At the end of the BERP chamber is a hexagonal ring that slides up over the vent holes to change the amount of resistance that the chamber offers.
Any brass player worth their salt knows that the instrument itself is basically a channeler and amplifier for the thing that really produces the instrument's vibration, which happens to be the human lips. A brass player spends the majority of their practice time developing control, range, flexibility, and tone quality of the brass embouchure in much the same way a vocalist works for control and ease of use of the vocal folds.
There are many schools of thought on the best approach to improving brass embouchure, but I along with many others definitely agree that "buzzing" on the mouthpiece alone develops the brass player's ability to control the buzz without the aid of the brass tubing as well as make the player responsible for listening to and controlling the pitch being produced by their lips. The other advantage of buzzing on the mouthpiece alone is that the buzz can be produced in a "sliding" fashion, producing any pitch within the comfortable tessitura of the player. When playing on the instrument, the player is limited in most cases to the frequencies that are resonated by that fixed length of tubing, hence the "partials" used in bugle calls.
The BERP allows the player to much more closely approximate the feel of blowing into their instrument while still benefiting from the flexibility of buzzing on the mouthpiece alone. Because the BERP is attached to the lead pipe of the instrument, the player still holds the instrument in the normal fashion so the weight against the face and proper habits of posture and breath support can still be maintained. Also, because it's attached to the instrument, it makes switching from playing to buzzing (or BERPing, as many band directors like to call it) very quick and easy, making it a great tool to hand out to an entire brass section.
One of the reasons that the BERP is such a great product is that there are a wide variety of applications for its use. BERPs are common sights on the brass lines of some of the top drum and bugle corps and marching bands in the country, as well as professional and studio musicians. BERPs are very useful for:
For brass sections, using a BERP provides a unified approach to buzzing on the mouthpiece. When players buzz on the mouthpiece alone, there are always variations in how the mouthpiece is held and how much pressure is placed on the lips from player to player, even if directors insist that they hold the mouthpieces in a uniform fashion. The BERP forces players to hold their instruments just as they would if they were playing normally, which reduces the variations in embouchure production. The resistance dial allows individual players to adjust the amount of resistance they feel depending on their own embouchure strength and the range of pitch they happen to be playing in.
The BERP can be used with any already existing brass exercise that emphasizes embouchure development. Use of books such as the Arban Conservatory Method for Trumpet can be accentuated by this tool. I use it with my beginners to establish proper tone at the very beginning. It puts ownership of sound production where it belongs - on the player, not the instrument.
The BERP comes in six different sizes for every major brass instrument. Click on the picture for more information on the size you are interested in and to make a purchase.
PLEASE NOTE: I am not a clinician, affiliate, or official endorser of this product. It is a fantastic product that I want to share with the readership of my website. If the good people who create this product had an affiliate program, I would be the first to sign up. The links I provide you here do, however, take you to my Amazon.com affiliate page where your purchases support the good people at BERP, Amazon, Brass and Woodwinds, and also ThomasJWestMusic.com - you are under no obligation to buy these products from me, but I would appreciate your support for the information I provide to you here and the time it took to create this webpage. Thank you for understanding.
Every BERP comes with a series of recommended exercises developed by the BERPs inventor, a professional jazz trumpet player. The exercises are a good starting point for use of the device. In addition, the good folks at BERP have put together a CD recording of all sorts of useful exercises. Click on the CD to get more information and get your own copy.
There is much more information on the BERP, its uses, sample exercises, and its inventor at the official BERP website. Inventor Mario Guarneri is a real down-to-earth guy who loves to help out band programs with bulk order discounts and so on. The BERP is a great product and if used regularly can truly help brass instrumentalists of all ages and ability levels improve their playing and enjoyment of their instrument. I hope you will take the opportunity to try one out.