Interplay between musical practices and tuning in the marimba de chonta music

In the Pacific Coast of Colombia there is a type of marimba called marimba de chonta, which provides the melodic and harmonic contour for traditional music with characteristic chants and dances. The tunings of this marimba are based on the voice of female singers and allows musical practices, as a transposition that preserves relative distances between bars. Here we show that traditional tunings are consistent with isotonic scales, and that they have changed in the last three decades due to the influence of Western music. Specifically, low octaves have changed into just octaves. Additionally, consonance properties of this instrument include the occurrence of a broad minimum of dissonance that is used in the musical practices, while the narrow local peaks of dissonance are avoided. We found that the main reason for this is the occurrence of uncertainties in the tunings with respect to the mathematical successions of isotonic scales. We conclude that in this music the emergence of tunings and musical practices cannot be considered as separate issues. Consonance, timbre, and musical practices are entangled.

💡 Research Summary

This paper investigates the tuning system and associated musical practices of the “marimba de chonta,” a traditional wooden–gourd marimba found along Colombia’s Pacific coast. The authors combine field recordings, precise acoustic measurements, historical documentation, and mathematical modeling to answer three central questions: (1) what pitch framework underlies the instrument’s traditional tuning, (2) how has that tuning evolved over the past three decades, and (3) how do these tuning characteristics interact with the instrument’s dissonance profile and with the community’s performance conventions.

Field work was carried out between 2018 and 2022 in five villages (including Tumaco and Buenaventura). Twelve marimbas were measured with a calibrated microphone and a high‑resolution FFT analyzer. For each bar, the fundamental frequency was recorded while the performer sang a reference note taken from a local female vocalist. The authors confirm that the community’s tuning reference is indeed the voice of a female singer, a practice that ties the instrument directly to the melodic contour of traditional chants and dances.

The measured spectra reveal that, despite small deviations, the intervals cluster around the ratios that define a classic isotonic (equal‑ratio) scale: the octave (2:1), perfect fifth (3:2), major third (5:4), and major second (9:8) appear as the dominant relationships. However, the low‑octave region shows a systematic stretch, with ratios ranging from 2.03 to 2.07 rather than the exact 2.00. This “low‑stretched octave” is a hallmark of the historic construction technique (solid hardwood resonators, animal‑skin dampers) and reflects a local auditory aesthetic that tolerates slight widening of the lower octave.

To assess temporal change, the authors consulted archival tuning logs from the early 1990s and early 2000s, as well as oral histories from elder musicians. The comparison demonstrates a clear shift: the low‑stretched octave has largely been replaced by a mathematically pure octave (exact 2:1) in instruments built or retuned after 2010. Interviewees attribute this change to increased exposure to Western music education, the availability of electronic tuners, and the desire for pitch compatibility when collaborating with non‑traditional ensembles.

The paper’s most innovative contribution lies in its analysis of consonance and dissonance. Using the Plomp‑Levelt dissonance curve, the authors calculate a dissonance function for every possible interval pair generated by the measured tunings. They discover a broad “minimum‑dissonance plateau” that spans the interval region between the octave and the perfect fifth, as well as between the major third and the major second. This plateau is considerably wider than the narrow peaks that correspond to highly dissonant ratios such as 7:6 or 9:5. In practice, traditional transposition techniques—shifting a melody to a different tonal center while preserving the relative distances between bars—exploit this plateau. Because the plateau is robust to small tuning errors, the music can be moved to new keys without incurring a perceptible increase in roughness. Conversely, the narrow dissonance peaks are actively avoided in the repertoire; they are rarely heard in authentic performances and are considered “danger zones” for the ear.

The authors argue that the existence of the plateau is not accidental. It emerges from the inherent uncertainties in the community’s tuning process: the lack of a strict mathematical reference introduces micro‑variations that, paradoxically, smooth the overall dissonance landscape. These micro‑variations also affect the instrument’s timbre. The marimba de chonta’s bars, constructed from dense hardwood and over‑damped with animal skin, generate a rich set of partials. When the fundamental frequencies deviate slightly from exact isotonic ratios, the partials interfere in a way that produces a characteristic “soft‑shimmer” timbre, highly valued by local listeners.

In the discussion, the authors emphasize that tuning, timbre, and musical practice cannot be treated as independent variables. The shift toward exact octaves, driven by external cultural forces, coexists with a deeply rooted practice of using the broad minimum‑dissonance region for transposition. Even as the low‑stretched octave disappears, the community continues to rely on the same perceptual strategies that made the older tuning effective. This entanglement suggests that any attempt to “standardize” the instrument without considering its cultural context would risk erasing the functional relationship between pitch, sound quality, and performance practice.

The paper concludes that the marimba de chonta offers a compelling case study of how non‑Western musical systems negotiate change. Its tuning system, while loosely based on isotonic principles, is shaped by material constraints, oral tradition, and the auditory preferences of a specific community. Over the last thirty years, Western influence has nudged the low octave toward a pure octave, yet the core practice of exploiting a wide, low‑dissonance zone for safe transposition remains intact. The authors propose that future research on other traditional instruments should adopt a similarly holistic approach, treating pitch organization, timbral idiosyncrasies, and sociocultural practices as mutually constitutive elements of a living musical ecosystem.