Timpani “Harmonicity”
Theoretically (and ideally), when a timpano’s head is well-tempered (also referred to as cleared or balanced) you should be able to strike the drum at any of the normal striking points around the circumference of the instrument and it should yield the same clear sustained pitched sound. A sound including a strong principal tone and many near-harmonic partials. The term fundamental should not be used to describe the pitch heard because it is not the fundamental. The fundamental frequency of the vibrating head actually detracts from the harmonicity of the timpano’s sound spectrum and the more that it can be suppressed, the stronger the sense of pitch the drum has (see Chapter 2: Circular Membranes).
Due to inconsistencies in the membrane material as well as the integrity of the tuck (the way it is attached to the flesh-hoop), you may find that certain areas will sound better than others for striking. For natural skins this is usually due to the following factors.
1) slight differences in thickness of the skin
2) the backbone: a natural nodal point (see Chapter 2)
3) an uneven tucking process
The backbone/hipbone areas in natural skins are physical anomalies, which disrupt the consistency of the membrane. Even when the skin is skived to a homogenous thickness, the elasticity of all parts of the membrane will not be uniform, especially in the backbone area. It is both a blessing and a curse. The curse is that it may limit the head to only a few resonant striking zones. The blessing is that when it evenly bisects the head, the backbone acts as a physical nodal point for (mode 1,1). This mode of vibration is what gives the drum its sense of pitch; it is called the principal tone. It is much easier to hear this mode when mounting and clearing natural skins, provided the backbone bisects the drum than it is when working with Mylar heads.
P.R. Kirby, The Kettle-Drums, 1930: “If the selected head contains a diametrical marking (the line of the backbone from the skin which it has been prepared), it should be placed at right angles to the line of the kettledrum stick when in position for striking.”
Charles L. White, Drums Through The Ages, 1960 “…and the head (mounted on the hoop) placed on the rim in a manner that the diametrical backbone line will run between two opposite tuning handles. This will position the head so the area the drumsticks will strike can be at right angles to the line of the animal’s backbone.”
Henry W. Taylor, The Art and Science of the Timpani, 1964 “…therefore I must respectfully differ from Professor Kirby. His opinion is that a point at right angles to the backbone line offers the best spot. My experiments and experience convince me that a point some four inches from one side of the neck end of the backbone line should be our first choice.”
Noted authors on the subject P.R Kirby: The Kettle Drums (1930), Charles L. White: Drums Through the Ages (1960), Henry W. Taylor: The Art and Science of Timpani (1964) all concurred that the head must be tucked and mounted so that the backbone splits the drum into two absolutely equal hemispheres. This was to assure that both halves of the skin would vibrate evenly. White and Kirby advocated finding a beating spot on the belly (some point perpendicular to the backbone) because the backbone is a natural nodal point for mode 1,1, where the principal pitch of drum is generated. Their belief was that a stronger pitch center was created when the drum was struck in this manner. Taylor was adamant that because of the way skins were manufactured at that time, certain parts of the skin had better “equality of tension” and “balanced impedance,” specifically the neck area. Speaking of backbone/neck area he writes, “Here, the animal continually stretched its neck to feed; the skin was made pliable and resilient during life and is pleasing to the immediate ‘feel’ of the stick. Which side of the backbone is best can only be judged by trial and error and by testing the balanced response from its ‘opposite’ at the butt.”
Fig. 1 (click to enlarge)
Figure 1 is the hypothetical mounting of a calf head for the drum to the direct right of the player. For this particular head, Area “A” on the neck proved to be the best playing spot. Backbone placement varies from player to player. Some place the backbone so it bisects the drum at lug points, others offset it a small amount. Some players prefer to mount a head so that the belly area is the primary striking spot. Others feel that the hip area usually has the best playing spots. No rules, just personal preferences; much depends on the integrity of the head itself, choice of primary playing spot(s), and the number of lugs a drum has (see below). Most modern calf heads (Kalfo) are homogeneous enough to have multiple playing areas, so a strict adherence to past mounting practices is not always necessary. Players often rotate their heads once a favored playing spot becomes tired and worn.
Cloyd Duff’s 32″ Anheier Cable Drum (Seven Lug)
belonging to Peter Kogan (retired) of the Minnesota Orchestra