Conical and Cylindrical Brasses
Bore Size and Flare
Brass Alloys and Finishes

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Conical and Cylindrical Brasses

Perhaps the most convenient classification of brass instruments is according to the extent to which they have a cylindrical or cone-shaped bore.  A cone-shaped bore is one in which the diameter gradually widens. The shape of the bore is important because it affects the quality of the sound and the degree of flexibility that can be attained.  Cylindrical and conical brass instruments are produced in soprano, alto, tenor and bass voicings.  The following table illustrates this:

 

Basic Types of Brass Instruments

Register	Cylindrical	Conical
Soprano	Trumpet	Cornet
Alto	Alto Horn (sometimes called Tenor Horn)	French Horn
Tenor	Trombone, Baritone	Euphonium
Bass	Sousaphone	Tuba

 

Cylindrical instruments do have some conical sections, of course.  The difference is a matter of degree rather than of kind. The trumpet -- usually regarded as a cylindrical instrument -- consists of a coiled tube about six feet in length, of which only about a third is really cylindrical.  The remainder is conical, except for the last 12 inches, which flares rapidly into the bell-shaped mouth.

With most brass instruments, the shape of the valves, the tuning slide and the section of tubing where the mouthpiece is inserted are all cylindrical. However, instruments such as cornets, euphoniums and tubas have a sufficiently greater proportion of conical tubing to ensure a noticeable difference in tone quality when compared to trumpets and trombones. Conical brass instruments have a more mellow sound than cylindrical ones.  They are also give the player greater flexibility.  This is because:

	A conical shaped standing wave tends to eliminate several upper partials, resulting in a less brilliant sound.
	Cylindrical tubing requires a more constant air stream speed.  In the case of inexperienced players, this can result in intonation problems, particularly when executing lip slurs.

The latter point is perhaps the most important reason why primary and lower secondary school concert bands are probably better off using cornets rather than trumpets in their brass sections, regardless of the preferences of the composer whose music they are playing.  Cornets are more flexible and easier to play.  They are also smaller, making them simpler to hold.  Their use should therefore make it easier for young students to develop a good posture and maintain reasonably good intonation.

The point seems worth making in view of the increasing emphasis here in Singapore in recent years on the sort of massive and penetrating sound from the ensemble that only trumpets can deliver.  Current fashion, in other words, does not favour the cornet.  Band directors who “go with the flow” on this issue are not necessarily operating in the true interests of their students, however.  At the very least, they will have to be prepared to spend more time on posture and embouchure training in order to ensure that their young trumpet players really are up to the challenge.

Of course, this recommendation in favor of cornets rather than trumpets does not extend to situations, such as in the scores of Alfred Reed and Philip Sparke, where composers call specifically for both instruments.  Music of the level of difficulty normally associated with such composers, however, is unlikely to be encountered by most primary or lower secondary school bands.

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Bore Size and Flare

Having advocated the use of cornets rather than trumpets for young bands on the grounds that they are somewhat easier to play, I hasten to add that this recommendation does not extend to the use of small bore instruments.  It is admittedly easier for beginners to produce an initial sound on small bore trumpets, cornets and trombones, but this is only because the student is not obliged to breathe properly.  Moreover, such instruments can be easily overblown at high dynamic levels.  The resulting distorted sound can be difficult to correct.

The flare of the bell can also have an important impact on tone quality.  A large flare has the effect of dampening the upper partials, thus producing a “darker” tone. This is especially so in the case of the French horn, which has a particularly small bore and a very wide flare.  Conversely, less flare gives a brighter tone by making the sound of the upper partials more obvious.

When selecting a brass instrument – be it a French horn, baritone, trombone or cornet – it is also important to remember that, while large and extra-large flares often give the impression of a fuller sound at close range, they often fail to project well in comparison with models having smaller flares. 

 

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Brass Alloys and Finishes

Brass instruments are made from up to four different materials: yellow brass, gold brass, red brass and nickel silver.  Each of these alloys is said to have an effect on the timbre, with those including a higher proportion of copper being associated with a darker tone. 

However, although widely believed by musicians, scientific experiment has repeatedly failed to support such an idea. I am repeating the concept here merely because the belief is so strongly held. The reality is that the real determinants of a brass instrument's timbre are its shape and the quality of workmanship that went into its manufacture.

Yellow brass (70% copper, 30% zinc) is perhaps the most widely used material.  Many players believe that it produces a bright, intense tone.  Some professionals, however, prefer the bells of their instruments to be made of either gold brass (85% copper, 15% zinc) or red brass. 

Gold brass is said to produce a broad, rich sound, while red brass is associated with soft mellow tones.  For many, nickel silver (70% copper, 20% zinc, 10% nickel) lacks the tonal richness of other brass alloys. The addition of nickel and the higher proportion of zinc does have the advantage of making the instrument stronger, however.  This implies that nickel silver is more appropriate for student models, since it is they that often have to survive rough handling. 

In practice, many instruments are actually made of two or more brass alloys.  It is not unusual, for example, for the lead pipes of even student model trumpets, cornets, euphoniums and tubas to be made of gold brass, partly as an insurance against corrosion or redrot, with nickel silver at stress points and bells consisting of yellow brass.   Trombones often use nickel silver on the inner slide and yellow brass on the outer one.  Bracings are typically made of nickel silver. 

Some professional players (notably trombonists) prefer lacquered finishes rather than silver plated ones on the grounds that the former offer a better response and a warmer tone. Silver coatings consist of real silver plating. Lacquer coatings use an epoxy lacquer that is sprayed onto a polished buffed brass surface to prevent it from tarnishing. Some more expensive instruments use gold plating. This is the ideal.  Although expensive, it doesn't tarnish and it looks great.

Lacquer finishes are best avoided in school bands.  Such finishes are not very durable, probably because they require more maintenance in the moist conditions of the tropics.  In apparent recognition of this problem, most student-line instruments are plated with hardwearing nickel silver.

An instrument’s mass is yet another issue. A heavy trumpet may be more difficult to play than a light one.  On the other hand, such a trumpet is believed to produce the darkest tone.  Conversely, a lightweight instrument will have a brighter tone and feel more responsive to the player.