What a rigorous scientific study would try to explain is WHY these tunings were made in such a way, what values shaped that decision and why it made any sense "to create beating on purpose" for that musical practice in that culture if that was the case and then test that hypothesis.So this group found that some of the tunings were probably done to create 'beating' on purpose.
What a rigourous scientific study would try to explain is "less stable" for whom, when and where? Perhaps in that culture "creating beating" is perceived or associated with "more stable", we don't know yet. That's the kind of things one would try to understand with the musicological approach, and that's why ethno is such an important part of it that cannot be dismissed.That's technically 'less stable'. It is probably supposed to be artistically less stable.
Again: music doesn't exist in a vacuum neither is an universal concept. It is historically constructed, socially mantained and individually experienced. As such one needs to understand the concepts, behaviours to understand the [sonic] results. Only then one can formulate hypothesis, test them and come up with theories to explain things. There are reasons for a gamelan to end up in Arizona in the first place!... One can know a lot of things about musical practices, but one must have the right questions first and then a solid methodology to address them and test the hypothesis.
«When the spectrum of a saron is combined with a harmonic tone, it generates a dissonance curve with minima near the steps of a pelog scale—the other essential scale in gamelan music.
Based on such observations, Sethares (2005) argued that musical instruments co-evolved with tuning systems and scales. Musical instruments that are played in combination with one another must be tuned in a way that supports their combination, and this approach to tuning gives rise to the scales that shape musical structure. Once a tuning system is established, a musical tradition can also support new instruments that have spectral properties consistent with that tuning system. This process of co-evolution explains why gamelan scales and their instrument timbres, which are so unique, are rarely combined with the scales of Western music.
In traditions that mainly employ instruments with harmonic spectra, the tuning systems that support the formation of consonant intervals are also compatible with pentatonic (six note) and heptatonic (seven note, diatonic) scales. According to some researchers and theorists, this correspondence explains why major and minor pentatonic and heptatonic scales are the most widely used scales in Western, Indian, Chinese, and Arabic music over the past several centuries (Gill & Purves, 2009; Sethares, 2005).
(....)
Because a high proportion of instruments produce periodic sounds, including the human voice, most scales permit intervals that have spectral properties that are similar to the harmonic series (and hence are low in dissonance [I'd ask: for whom?]). However, traditions such as Javanese gamelan music that use inharmonic instruments have very different scales. The slendro and pelog scales permit intervals that are not similar to the harmonic series but that are predictable from the spectral properties of the instruments used in that tradition.
(...)Relative changes in pitch are salient sources of information in both music and speech. Unlike speech, music focuses on a collection of discrete pitches. Simultaneous and sequential combinations of these pitches occur extensively in music and are highly meaningful. Simultaneous intervals differ in the level of consonance and dissonance they produce. Consonant intervals such as the octave and fifth have many partials in common, and those that are unique are seldom within a critical band and do not give rise to roughness. Sensory factors constrain preferences for musical intervals, but early preferences can also be modified by learning and enculturation (see also, Guernsey, 1928; McLachlan, 2011).
Sequential intervals are the basis for melody. Whereas simultaneous intervals are constrained by processes related to consonance, dissonance, and fusion, sequential intervals are subject to constraints of auditory streaming. Music generates significant interactions between these types of intervals: fusion between simultaneous intervals can be avoided by emphasizing horizontal structure, allowing listeners to perceive individual voices in polyphonic music and reducing any potential dissonance between concurrent tones.
Mechanisms underlying melody processing may be engaged for domains other than music, such as speech intonation. Indeed, the capacity to extract contour may be a general property of the auditory system. Whether interval perception has a special status in the auditory system remains unclear. Our perceptions of the pitch distances in intervals are susceptible to a wide range of extraneous influences, including timbre, pitch register, direction of pitch change, tonal context, and visual signals arising from performers. Intervals also vary in performance when variable-pitch instruments are used. Such changes depend on both the technical skills and the expressive intentions of performers. Expressive intonation is detectable but does not tend to alter the perceived interval category.
Scales enable precise distinctions between interval sizes. Trained and untrained listeners are highly sensitive to scales and can even sing an underlying scale after hearing just a few notes of music. During music listening, however, understanding of scales may be less important than mechanisms of statistical learning. Because scale development depends on instrument timbres, there is no one ideal scale or tuning system. For music that emphasizes instruments with harmonic spectra, scales tend to permit the formation of intervals such as the octave, fifth, and third—intervals also found in the harmonic spectra of periodic sounds. For music that emphasizes instruments with inharmonic spectra, scales permit other intervals that reflect those spectra. Nonetheless, most scales throughout history and across cultures are predictable from the harmonic series, reflecting the prevalence of harmonic spectra in musical instruments, including the human voice.» - William Forde Thompson, in Deutsch, Dianne, The Psychology of Music, 3rd Ed.
So this leaves us with a possible explanation and a question: does growing in cultures whose instruments reflect inharmonic spectra change the meaning of dissonance [roughness] and how this quality is perceived?
