The transverse flute works most efficiently when the embouchure piece or joint has wall thickness sufficient enough for the embouchure hole to be adequately undercut. This practice, making the hole larger on the inside than on the outside of the instrument, addresses several acoustical problems without requiring mechanical devices. Undercutting is critically important, for while it enables both fingerholes and embouchure to be large enough at the bore to produce optimum voicing, pitch and volume, it allows those same holes to be small enough in their surface dimensions to be covered by the fingertips or, in the case of the embouchure, to accommodate the player's airstream to the best advantage. Such adjustments cannot be taken very far on simple folk instruments with thin walls, but the design of European transverse flutes traditionally includes adequate wall thickness for wood, ebonite (hard rubber), and ivory instruments to achieve proper embouchure hole dimensions. For sheet metal instruments the wall thickness is increased at the embouchure in either of two ways, as follows:

The earlier form involves an "embouchure barrel" which surrounds the sheet metal tube of the head joint at its embouchure hole with a short cylinder of wood or ivory, increasing the outer diameter to that of a typical wood or ivory head joint. The embouchure is bored and undercut as if made from one material. The Miller Collection has splendid examples such as two of the earliest of Theobald Boehm's 1847 model cylindrical bore flutes, DCM no. 652, with a boxwood embouchure barrel, and DCM no. 470, with an ivory embouchure barrel. A slightly later variation of this earlier form involved a three-part sandwich of materials which added at the barrel an outer metal veneer, usually of the same metal as the instrument, that was closed neatly or decoratively at each end around a middle layer which is visible only at the embouchure hole. In some cases the inner wood or other material is omitted leaving a thermally useful airspace with the embouchure hole and undercutting achieved by soldering in a tapered tube of the necessary dimensions.

Detail of DCM#: 470 Embouchure barrel.	Detail of DCM#: 43 Embouchure barrel.	Detail of DCM#: 161 Embouchure.

A still slightly later version of the same soldered embouchure hole tube assembly involves an "embouchure plate" which eliminates most of the embouchure barrel, leaving only a large, usually oval, plate containing the embouchure hole and standing a few millimeters above the surface of the head joint tubing. The embouchure hole tube (the "riser") has a small bottom flange large enough for soft soldering the entire unit (if all metallic) to the head joint. It is this arrangement which is encountered on most modern metal flutes. Early versions used other materials for the plate and therefore required mechanical joining rather than soldering, usually with a pair of decorative screws joined to tapped lugs soldered to the body tubing.

"Lip plate" refers to any sheet metal veneer, usually an oval (often inlaid flush with the outer surface of the head joint) which surrounds the embouchure hole of a wooden or other non-metal flute. It may be cemented and/or tacked to the tubing.

Detail of DCM#: 449 Lip plate.	Detail of DCM#: 73 Lip plate ferrule.

"Lip plate ferrule" refers to a variation of the lip plate, which encircles the head joint at the embouchure area with a sheet metal cylinder resembling the embouchure barrel and usually recessed flush with the outer surface. The lip plate and lip plate ferrule for nonmetal flutes were additions for presenting a metallic embouchure surface for those players who preferred it. The lip plate ferrule was also sometimes applied to reduce cracking of the wood. In some cases, an entire nineteenth- or early twentieth-century wooden head joint may be sheathed with a sheet metal veneer, usually nickel silver. Such instruments are usually metal-lined, frequently with a double metal tube forming a tuning slide within the two-part head joint. The lower of those two sections is termed the "barrel" or "head joint barrel," its slightly bulbous exterior usually appearing similar to the barrel joint of a clarinet. The embouchure barrel and embouchure plate of metal flute head joints may provide the player with a more attractive material for the embouchure, such as gold or gold plate, but their main purpose is to improve the acoustical properties of the instrument through greater wall thickness at the embouchure.

"Thinned" or "Thinned wood" refer to a process developed in the nineteenth century to reduce the wall thickness of cylindrical bore wood flutes, thereby supposedly increasing the vibrancy of the tube. Similar to the earlier method of cutting key blocks (discussed later), it required a high degree of careful handwork in addition to those aspects of an instrument which could be finished by machine. After drilling the bore, the outer dimension was turned on a lathe to achieve a fairly thin wall between toneholes or above or below tonehole groupings. This process left wider outer diameter turnings or beads between those thinned areas, each of which would be bored for a tonehole seat made of the body wood or other material. The rest of each such bead or ferrule--well over half the circumference of the tube--would be cut away and finished by hand. Only the head joint was relatively easy to finish, requiring only one such hand operation where the embouchure plate was left standing from cut-away material.

Detail of DCM#: 24 Integral Tone Hole Elevations.

Thinned wood flutes were very expensive due to the handwork and time required, and consequently they are rare. Perhaps the most impressive example in the Miller Collection is DCM no. 24, an unfinished boxwood alto flute in G (bass) by Boehm & Mendler (see "Flute Misnomers.") It is unfinished only with respect to its keywork which was never applied to the instrument. The wood thinning is thus all the more convenient to examine.

Conventions and Definitions