Creating Tension I--Technologies for Attaching Drumheads to Shells

The sound a drum puts out when played is shaped by several interacting variables: the material, thickness, diameter, mass, structure, and tautness of its membrane/s; the shape of its shell and the internal resonating space it articulates; the physical details of the beater/s used to transfer energy into its drumhead/s; and where on the surface of the drumhead/s the beater/s make contact. The presence and distribution of tension in a drumhead is very important to the musical use of a drum, but this feature is basically invisible. However, there are visible design features on any drum that can communicate just how tautness is created and regulated on its drumheads. This essay concentrates only on the subject of drumhead attachment to drum shells, the designs, processes, and mechanisms that have been devised and applied by drum makers the world over to create musically useful tension in drumheads. But first we need to present a few basic observations about the acoustics of stretched membranes.

Basics of Membranophone Acoustics

A taut drumhead and its sound-producing area--usually (but not always) a circular field the edge of which is established by the rim of the drum shell opening against which the membrane is pressed--when excited by striking or rubbing responds by vibrating in complex modes of movement. Both transverse waves and circular ripples are simultaneously generated in the membrane each of which contributes a frequency to the mix of frequencies that we hear and identify as a particular drum sound. The specifics of the drumhead material--its source material, its thickness, its mass, its dimensions--along with the amount and distribution of tension on the membrane and with what it is struck will shape a drumhead’s mix of vibrational modes and how it is perceived by the listener. This vibrational/frequency mix is usually so complex that the sound given off does not give rise to the perception of a definite pitch. Although drum makers in some cultures have found ways to design and mount drumheads and to shape the resonating space of the shell that supports them to give rise to the perception of definite pitch in vibrating drumheads, the vast majority of drum designs produce indefinitely-pitched sounds. But even indefinitely-pitched drums do not all sound alike, for a listener can learn to discern between the distinctive sound qualities of a range of drums. And although this discernment is not entirely dependent on how a drum’s membrane/s is/are attached, attachment techniques play a significant role in shaping the distinctiveness of a drum’s sound.

Drumhead Attachment Methods

Both animal skins (fish and reptilian skins and mammalian pelts and rawhides) and thin single- or double-ply sheets of manmade synthetic material (nylon, Mylar, Kevlar, and other polymer plastic compounds) are used as drumheads. Whatever material is used, it must ultimately be stretched over the rim of a drum shell opening and held in a state of tension before being musically useful. The mechanisms for drumhead attachment, for creating and controlling drumhead tension, are numerous and will be discussed here in two groups differentiated from one another on the basis of drumhead design--whether the drumhead is frameless or its edge is reinforced with some sort of framing.

Unframed Membranes

An unframed membrane is one that has no frame-like supplemental strengthening of its circumference. Such a drumhead must have a greater diameter than the shell opening it is to cover, and it is to this excess edge material that the mechanisms for creating and sustaining head tension are applied. Generally speaking only animal skin membranes can be used for unframed drumheads, and this is because a crucial part of the attachment process involves them being stretched while in a moistened state (plastics do not stretch when moistened). A soaked animal membrane when affixed to a shell and allowed to dry will become more taut. Thus the basic level of tension for an unframed drumhead is set at the time of manufacture and any further adjustment to that tension is generally made at the time of performance either by moistening the membrane to reduce the tension and lower its pitch or by placing it near a heat source to dry it out, which increases its tension and raises its pitch. Two basic techniques used to set the tension of unframed heads are direct fastening and direct lacing.

        Direct fastening

The circumference of a moist unframed membrane may be glued (image #1), tacked/nailed (image #2), or pegged (image #3) directly to the drum shell, usually against a circular band of the shell’s outside surface just below the rim of the shell opening that is being covered. The drum’s shell, along with the fastening agent, provides the counterforce to the tension created in the head by the drum maker while stretching and attaching the moist membrane, and this tension is increased further as the drum head dries out.

        Direct lacing

A long length of lacing passes through closely spaced perforations located around the circumference of the membrane and in turn around or through some resistance creating component of the instrument such as a peg imbedded in the shell (image #4), a leather belt that in turn is attached to the drum shell with pegs or nails (image #5), the waist of the shell (image #6), or perforations in the edge of a second drumhead (image #7). The drum’s shell or the direct connection to a second head, along with the fastening agent (the lacing), provides the counterforce to the tension created in the head by the drum maker who pulls the lacing as taut as possible while stretching and attaching the moist membrane (or membranes), and this tension is increased further as the drum head/s dries out.

Framed Membranes

A framed membrane is one that has a frame-like supplemental reinforcement of its circumference. The frame of such a drumhead must have a greater diameter than the shell opening it is to cover, and it is to the frame itself that the mechanisms for creating, sustaining, and modifying head tension are applied. Both animal skin and manmade materials can be used for framed drumheads, and their frames are typically in the form of a hoop made of rope (image #8), rawhide (image #9), rattan (image #10), wood (image #11), or metal (image #12). Membrane frames can therefore vary considerably in their rigidity, but they all contribute significantly to the desirable result of tension equalization over the drumhead surface.

The edge of a membrane must be somehow wrapped or sewn around or tucked, pinched or woven into its frame. We will discuss the wide range of specific framed-membrane attachment mechanisms encountered in this collection of membranophones in two groups differentiated from one another by how the tension creating device contacts the membrane frame: 1) indirect lacing, where tension lacing repeatedly passes over a membrane frame and, usually, through holes punctured in the membrane itself; and 2) tension collar/rim, where the tension creating device includes a stiff collar or rim that fits over the membrane hoop--lacing or hardware is attached to the collar/rim, not directly to the membrane or its hoop. Regardless of the basic nature of the attachment mechanism captured in the above-mentioned distinction, there must be designed into a membranophone a means to create a counterforce against which the tension mechanism works. This feature of drum design will be discussed in the paragraphs to follow, as will the ways in which tuning control (fine adjustments to drumhead tension) is achieved. [A quick note about terminology: while somewhat standardized terminology exists in the West in regard to naming components of drumheads and attachment mechanisms, we have found it necessary to modify this vocabulary to make it applicable to membranophones worldwide. Every effort will be made to clearly define the terminology as used on this site.]

        Indirect lacing

A long length of lacing passes sequentially through equidistantly-spaced perforations in the membrane just inside the head’s frame and then over the frame itself. Between these passes over the membrane frame the lacing passes over, around, or through some resistance creating component of the instrument such as pegs imbedded in the shell (image #13), a ring (of rope, rawhide, rattan, metal) serving as a counterhoop with a diameter smaller than that of the greatest diameter of the drum shell between it and the membrane frame (image #14), or the membrane frame of a second drumhead (image #15). The drum shell’s shape or a peg projecting from it, or the direct connection to a second framed head, along with the fastening agent (the lacing), provides the counterforce to the tension created in the head/s by the drum maker who pulls the lacing as taut as possible while stretching and attaching the moist membrane (or membranes), and this tension is increased further as the drum head dries out.

On many membranophones with indirect lacing the performer will have some control over fine tuning the amount and equalization of tension on the instrument’s head/s. Some of the mechanisms that make this possible are: sliding pegs that penetrate the drum shell (image #16); wedges placed between the shell and a counterhoop (image #17); slidable dowels pinched between the lacing and the drum shell (image #18); and slidable rings around consecutive passes of the lacing as it runs back and forth between two membrane frames (image #19) or a membrane frame and a counterhoop (image #20). All of these mechanisms in one way or another allow the musician to increase and decrease the pull of the lacing on the membrane frame/s and, ultimately, on the degree and distribution of tension in the drumhead/s. 

        Tension collar/rim

A common method of attaching framed heads to drum shells involves the use of a stiff collar or rim that fits over the membrane frame and to which the mechanisms of tension control are attached. In Western parlance this type of collar is called a ‘counterhoop’, but we are employing this term for a ring- or hoop-like agent of counterforce that encircles the drum shell. Tension collars are made in varying forms--a ring (image #21), a hoop (image #22), or a flanged or folded hoop (image #23)--but will always have the same diameter as the membrane frames over which they are positioned.

A tension collar must be linked to something that provides a counterforce--either a counterhoop encircling the drum frame (image #24), brackets/anchors firmly attached to the side of the drum shell (image #25); or the tension collar for a second drumhead (image #26)--with lacing (image #27) or metal rods with at least one of their ends threaded to accept a nut (image #28).

The lacing used to apply the downward pull on the tension collar and, in turn, the framed membrane passes over the top edge of the collar (image #27). One end of a metal tuning rod may be hook-shaped and hooked over the top of a collar hoop (image #22) or a collar ring (image #21) or through a hole in the side of a flanged collar (image #23). The top end of some tension rods is shaped so as to block it from passing through a hole in a stub attached to the outside edge of a collar through which the rest of the rod passes (image #29).

The following series of images illustrates how a framed membrane is attached to a cylindrical drum shell using a flanged/folded tension collar and metal tension rods. In image #30 we see the various attachment components laid out--the drum shell with one uncovered opening is in the background; in the foreground from left to right are the framed membrane (the drumhead with its rigid flesh hoop), eight tension rods, the tool used to screw the tension rods once they are installed, and the flanged/folded metal tension collar. In image #31 the flesh hoop has been placed over the opening in the shell (the interior diameter of the membrane flesh hoop is slightly greater than the exterior diameter of the shell opening). The flanged tension collar has been placed over the drumhead in image #32; the flat area between the two folds in this hoop rests precisely on top of the drumhead’s flesh hoop. In image #33 the tension rods have been slid through the holes around the circumference of the flanged tension collar. The bottom, threaded, end of each is screwed into a lug nut housed in a metal bracket that is securely attached to the side of the drum shell. The top end of each rod has a bolt-like head that is wider than the hole in the tension collar through which the rod passes. By using the tuning tool to torque the bolt-head end of a rod, its threaded end is screwed further into the counterforce-producing bracket on the shell. When this tightening action is applied to all eight tension rods sequentially, the tension collar pushes down with increasing but equalized force on the drumhead flesh hoop, stretching and making more taut the playing surface of the membrane.

Bibliography

Campbell, Murray, Clive Greated, and Arnold Meyers. 2004. Musical Instruments: History, Technology, and Performance of Instruments of Western Music. Oxford: Oxford University Press.

Waring, Dennis. 2003. Making Drums. New York: Sterling Publishing Co., Inc.

(by Roger Vetter)