# Roughness and consonance

When two notes are a little further apart, the beats become too fast to count, and the sound turns grainy or buzzy. This is roughness. In 1863 Hermann Helmholtz proposed that it explains why some intervals sound smooth and others tense. With simple ratios like the octave and the fifth, many harmonics of the two notes coincide exactly. With an interval like the semitone, many harmonics land close to each other and rub. Whether people enjoy roughness is another question. Some traditions look for it, and listeners who grew up far from Western music do not always prefer the smooth intervals. verify

Connects to:
- [Beats](https://mapideas.org/i/mu_beats)
- [The harmonic series](https://mapideas.org/i/mu_harmonics)
- [The fifth](https://mapideas.org/i/mu_fifth)
- [Gamelan and ombak](https://mapideas.org/i/mu_gamelan)
- [Chords and voice leading](https://mapideas.org/i/mu_chords)

Sources:
- [Wikipedia: Consonance and dissonance](https://en.wikipedia.org/wiki/Consonance_and_dissonance)
- Plomp and Levelt (1965), Tonal consonance and critical bandwidth, JASA 38, 548 to 560
- McDermott et al. (2016), Indifference to dissonance in native Amazonians, Nature 535, 547 to 550
- [What is music? Module 3, why some intervals sound smooth and Lab 3b](https://sofiagallego.com/what-is-music/)

Source: https://mapideas.org/i/mu_roughness · open on the map: https://mapideas.org/#mu_roughness