The Problem: When the Fifth Takes Over
When you strike a well-tempered timpano in the normal playing area, you are exciting a set of vibrating membrane modes called the preferred diametric modes. At the same time, the normal playing spot tends to minimize the excitation of the lowest concentric modes, which are less useful for producing a stable timpani pitch. Any low concentric energy that is excited is strongly coupled to the air/bowl system and tends to decay quickly, leaving the preferred diametric modes to define the musical pitch.
The issue discussed on this page is not that the fifth is “bad.” Mode (2,1), the fifth, is an important part of timpani tone. The problem occurs when the principal tone, mode (1,1), is weak, uneven, or decays too quickly. When that happens, mode (2,1) can become too prominent in the decay and pull the listener’s ear away from the intended pitch center. This is what many timpanists experience as an overbearing fifth or pitch creep.
Principal Tone vs. Lowest Physical Mode
The lowest physical mode of the membrane is concentric mode (0,1), but it is not the musical pitch of the timpano. The sound humans hear as the pitch of the drum is the principal tone, associated most closely with diametric mode (1,1). From a musical perspective, this principal tone should not be casually called the fundamental, because the lowest physical mode of the membrane is not the pitch around which the timpano’s useful near-harmonic structure is organized.
In essence, the spectrum of a timpano’s sound is made of a group of secondary quasi-harmonic overtones surrounded by an initial core of noise. The ear accepts this group of preferred modes as a convincing pitch, even though the timpano is not producing a true harmonic series in the same way a string or wind instrument does.
The Role of the Bowl and Air Loading
Another important phenomenon occurs because of the attached bowl. The bowl creates a baffle and an enclosed air volume, both of which affect how the vibrating head radiates sound. This is a good thing because it helps suppress the naturally dissonant lowest physical mode of the vibrating membrane, mode (0,1). However, the same bowl/head interaction can also shorten the decay of the principal tone, diametric mode (1,1), to some extent.
Fig. 3l
Figure 3l charts the decay times of the lower mode frequencies of a timpano both with and without the bowl. Without the bowl, the modes are generally less efficient at radiating their energy, so they have longer decay times. At first, this may seem desirable. However, that longer decay also includes the inharmonic lower concentric modes, not just the preferred pitch-bearing modes. With the bowl in place, many of the lower modes radiate energy more efficiently and decay faster. When a timpano is struck in the normal playing area, roughly a quarter of the distance between the edge and the center, the less pitch-useful modes tend to die away quickly enough for the preferred modes to dominate the sound spectrum.
Too much damping or weakness in the principal tone, mode (1,1), is not a good thing because it can lead to the overbearing fifth and pitch creep. This occurs when the principal tone does not have a strong, focused, and sustaining presence in the spectrum. The objective when tempering a head, also called clearing or balancing, is to adjust the tension of the membrane so that the principal tone speaks clearly and remains the strongest pitch reference for the ear.
Why Mode (2,1) Can Mislead the Ear
With mode (1,1) functioning as the principal tone, the next important quasi-harmonic partial is mode (2,1). When vibrating in the (2,1) mode, a circular membrane acts much like a quadrupole source. A quadrupole source is less efficient at radiating energy than the (1,1) dipole source and much less efficient at radiating energy than the (0,1) monopole source.
Because mode (2,1) radiates energy less efficiently than the lower modes, it can decay more slowly and remain audible after the principal tone has begun to fade. This longer persistence is one reason the fifth can become perceptually dominant. Mode (2,1) contributes significantly to the musical sound of the drum, but if the principal tone is weak or unstable, the fifth can begin to sound like the controlling pitch.
The mistake many people make when tempering heads is listening too intently to mode (2,1) instead of focusing on mode (1,1). This happens naturally because:
1) the bowl/head system can cause mode (2,1) to remain noticeable after mode (1,1) begins to decay,
2) mode (2,1) radiates its energy less efficiently, so the sound it creates can take longer to decay, and
3) mode (2,1) is a strong component of the overall perceived pitch and sustain of the drum.
The listener must learn to identify and favor mode (1,1) while allowing mode (2,1) to support the sound without taking over the pitch center. Mode (2,1) should be present in the spectrum, but it should not become the dominant pitch impression. This kind of listening can take years of practice to master when tempering by ear alone.
Since mode (2,1) can persist longer than mode (1,1), it may add sustain to the sound, which is desirable. However, don’t be deceived by this sustain. Mode (2,1) can become a wolf in sheep’s clothing if you follow it too closely. Its sustain may sound attractive even while it pulls the ear away from the true principal-tone center.
What the Overbearing Fifth Sounds Like
The symptom is not merely that the fifth is audible. A healthy timpano will include mode (2,1). The problem occurs when the principal tone fades too quickly or lacks focus, allowing the fifth to become the dominant pitch impression during the decay. The listener may hear the pitch seem to rise, lean upward, or drift away from the intended center.
When the frequency of the principal tone, mode (1,1), is not strong and consistent from lug to lug, the overall strength of perceived pitch is severely diminished. In that situation, permutations of the more audible mode (2,1), the fifth, can dominate the spectrum. An overbearing fifth generates a pitch shift once the principal tone begins to decay.
This is also why the primary playing channel and the secondary/orthogonal channel matter. If mode (1,1) is not stable across both channels, mode (2,1) can become disproportionately noticeable. The drum may seem to sustain well, but the sustain is not centered. Instead of supporting the principal tone, the fifth begins to pull the pitch away from it.
The graphic below shows the prominence of mode (2,1), the fifth, in a normal timpano spectrum. Once the overbearing fifth becomes pervasive, it can quickly mask the other preferred modes because it remains audible in the decay and can dominate the listener’s perception of pitch.
Waterfall chart (frequency, time and amplitude) of a timpano sound spectrum
(single struck note) highlighting six preferred modes (1,1), (2,1), (3,1), (4,1), (5,1) and (6,1)
(Fleischer & Fastl)
Head Wear, Tension History, and Synthetic Heads
The overbearing fifth is especially noticeable once a head becomes worn or becomes out of clear. It can also happen if a head has not been tempered properly during the initial mounting and is then continuously played. In that case, the head may become unevenly stretched over time, making the principal tone harder to stabilize and allowing mode (2,1) to dominate the decay.
Natural skin and synthetic heads fail differently. Skin heads are affected by biological unevenness, backbone structure, thickness variation, and humidity. Synthetic heads are affected by film orientation, creep, dimples, bearing-edge crease fatigue, and tension history. Once a synthetic head has been mounted, stretched, seated, played, cycled through the range, dented, heated, or bent over the bearing edge, it carries a tension history. That history can make mode (1,1) harder to stabilize and can allow upper partials, especially mode (2,1), to become more noticeable than they should be.
Once a synthetic head is consistently stretched in a way that allows the overbearing fifth to dominate the spectrum, it is often best to replace the head and temper the new head properly. Continued adjustment may improve the problem temporarily, but if the material itself has developed uneven tension history, the head may no longer be able to support a stable principal tone across the full range.
Excessive stretching, repeated flexing, impact damage, and heat can all shorten the service life of a Mylar or PET head. The bearing-edge crease is especially vulnerable because it has been bent, clamped, rubbed, and tension-cycled over the life of the head. This is one reason used synthetic heads usually do not remount successfully: the collar crease has formed under one specific bowl shape, seating pattern, and tension history. Once removed, it rarely reseats with the same symmetry.
Heat guns, hair dryers, irons, and other localized heat sources can create uneven shrinkage and new stress patterns in PET/Mylar film. Even if the head looks improved temporarily, the treatment can make pitch stability worse by introducing localized tension imbalance. A head that has severe dimples, bearing-edge crease damage, or persistent fifth dominance is usually giving a structural warning, not merely a tuning complaint.
What to Do About It
If a head replacement with correct tempering is not an option, the overbearing fifth can be mitigated to some degree by following Step No. 5 and Step No. 6 found in Chapter Five.
In practical terms, the player should return attention to mode (1,1). Check whether the principal tone is stable at the lugs, whether it remains consistent across the primary and secondary/orthogonal channels, and whether soft and loud strokes share the same pitch center. If the drum sounds sustained but the pitch seems to lean upward or drift after the attack, the fifth may be taking over.
When the head is properly mounted and tempered, the virtual pitch of the preferred modes convinces the human auditory system that it is hearing harmonic pitch, even though the timpano is producing a managed near-harmonic compromise rather than a true harmonic series.
Final Practical Takeaway
The fifth is part of a good timpani sound, but it should support the principal tone rather than replace it. When mode (1,1) is strong and stable, mode (2,1) adds color, resonance, and sustain. When mode (1,1) is weak, uneven, or decays too quickly, mode (2,1) can become an overbearing fifth that pulls the pitch center away from the note the player intended. The cure is not to eliminate the fifth, but to restore the authority of the principal tone.