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8 How Brass Instruments Are Made
note in tune. The ‘compensating’ valve system automatically improves intonation
by running the additional tubing of a master valve (that giving the greatest lowering
of pitch) through separate passages in the other valves; these then add the required
extra length of tubing when used in combination with the master. Compensating
valves are used on some french horns and many euphoniums and tubas. The ‘double
principle’ used in ‘full double’ french horns uses alternative rather than additional
valve loops for the valves other than the master: this makes for a heavy instrument,
since typically three valves each have two full-length valve loops; so as a result it
has rarely been used on tubas, but it is the preferred valve pattern for french hornys.
The position of the valves on the tubing is a matter of design preference for
instruments with a substantial amount of cylindrical tubing such as the french
horn. Recent research by Gregor Widholm (2005) has shown that this can have a
significant effect on the smoothness of slurred transitions from one note to another
that involve a change in the valves operated.
Piston and rotary valve cases are turned on a lathe and machined to size, and then
the ports are drilled. Small pieces of tubing which connect two valves, or each valve
with the rest of the instrument (the ‘knuckles’), are inserted in the holes, and the
whole assembly (‘valve cluster’) of three or four valve cases with connectors and
knuckles is wired together and soldered at the same time. Valve pistons are made
of hollow construction for lightness: the body is often produced by deep drawing,
and the ports are then drilled to take the internal passages (‘coquilles’) which are
inserted through the drilled holes and silver-soldered into place. Protruding tubing
is then removed, and the piston is fitted by a process of reaming the inside of the
case, grinding the piston and lapping. To prevent a piston from rotating, a lug (the
‘key’) projects from the piston body and runs in a vertical channel (the ‘keyway’)
cut into the case interior. Valve rotors are made by a similar process, though on
cheaper instruments they can be cut from solid brass or bronze.
8.5 Assembly
Before an instrument is assembled, the parts are cleaned. Small pressed parts are deburred manually or in a vibrating bath. The instrument is assembled starting from
the bell or the next largest section and working towards the mouthpipe. Straight
sections (‘branches’), U-bends (‘bows’), and other sections are joined by soldering;
each joint is covered by a sleeve or ‘ferrule’. An instrument can be left with its brass
polished (sometimes referred to as ‘raw’ brass) which over time gradually acquires
a patina if not repeatedly polished, but most instruments are given some kind of
surface protection after polishing to preserve their appearance longer. Silver-plating
by electrolysis has been offered as a standard option by many makers since the
mid-nineteenth century and gives a brilliant, easily-cleaned surface. This adds a
protective layer of silver so thin that the acoustical properties of the instrument are
not perceptibly affected. Other instruments are sprayed with clear or tinted lacquer,
which can preserve the colour of brass but which adds a thin coating to the metal
8 How Brass Instruments Are Made
note in tune. The ‘compensating’ valve system automatically improves intonation
by running the additional tubing of a master valve (that giving the greatest lowering
of pitch) through separate passages in the other valves; these then add the required
extra length of tubing when used in combination with the master. Compensating
valves are used on some french horns and many euphoniums and tubas. The ‘double
principle’ used in ‘full double’ french horns uses alternative rather than additional
valve loops for the valves other than the master: this makes for a heavy instrument,
since typically three valves each have two full-length valve loops; so as a result it
has rarely been used on tubas, but it is the preferred valve pattern for french hornys.
The position of the valves on the tubing is a matter of design preference for
instruments with a substantial amount of cylindrical tubing such as the french
horn. Recent research by Gregor Widholm (2005) has shown that this can have a
significant effect on the smoothness of slurred transitions from one note to another
that involve a change in the valves operated.
Piston and rotary valve cases are turned on a lathe and machined to size, and then
the ports are drilled. Small pieces of tubing which connect two valves, or each valve
with the rest of the instrument (the ‘knuckles’), are inserted in the holes, and the
whole assembly (‘valve cluster’) of three or four valve cases with connectors and
knuckles is wired together and soldered at the same time. Valve pistons are made
of hollow construction for lightness: the body is often produced by deep drawing,
and the ports are then drilled to take the internal passages (‘coquilles’) which are
inserted through the drilled holes and silver-soldered into place. Protruding tubing
is then removed, and the piston is fitted by a process of reaming the inside of the
case, grinding the piston and lapping. To prevent a piston from rotating, a lug (the
‘key’) projects from the piston body and runs in a vertical channel (the ‘keyway’)
cut into the case interior. Valve rotors are made by a similar process, though on
cheaper instruments they can be cut from solid brass or bronze.
8.5 Assembly
Before an instrument is assembled, the parts are cleaned. Small pressed parts are deburred manually or in a vibrating bath. The instrument is assembled starting from
the bell or the next largest section and working towards the mouthpipe. Straight
sections (‘branches’), U-bends (‘bows’), and other sections are joined by soldering;
each joint is covered by a sleeve or ‘ferrule’. An instrument can be left with its brass
polished (sometimes referred to as ‘raw’ brass) which over time gradually acquires
a patina if not repeatedly polished, but most instruments are given some kind of
surface protection after polishing to preserve their appearance longer. Silver-plating
by electrolysis has been offered as a standard option by many makers since the
mid-nineteenth century and gives a brilliant, easily-cleaned surface. This adds a
protective layer of silver so thin that the acoustical properties of the instrument are
not perceptibly affected. Other instruments are sprayed with clear or tinted lacquer,
which can preserve the colour of brass but which adds a thin coating to the metal