# Major 7th interval vs octave or third-octave interval **URL:** \ **Category:** Uncategorized\ **Created:** [February 10, 2023, 10:40am UTC](https://lookmumnocomputer.discourse.group/t/major-7th-interval-vs-octave-or-third-octave-interval/5903 "2023-02-10T10:40:47Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [February 10, 2023, 1:49pm UTC](https://lookmumnocomputer.discourse.group/t/major-7th-interval-vs-octave-or-third-octave-interval/5903/2 "2023-02-10T13:49:02Z")
That’s also mentioned here: > [@YuSynth Fixed Filter Bank (with AO modifications)](https://lookmumnocomputer.discourse.group/t/yusynth-fixed-filter-bank-with-ao-modifications/4129): > > This is a somewhat modified version of Yves Usson’s Fixed Filter Bank [module](https://www.yusynth.net/Modular/EN/BANK/index.html) in Kosmo format. Usson’s FFB’s functionality and front panel design are based heavily on the Moog 914. Both have a low pass filter and a high pass filter, and in between, twelve band pass filters. The input goes in parallel through all fourteen filters and the resulting outputs are mixed to form the module output, with a knob for each filter to attenuate its contribution to the mix. (This sounds rather lik… If you consider the Moog 914 fixed filter bank it’s based not on octaves or third-octaves but half-octaves, the same issue. The two lowest frequencies it uses correspond roughly to the notes B natural and F natural, a half octave apart. Moreover the higher pitches correspond to B natural and F natural in higher octaves since they’re multiples of half octaves. So pitches near those two would tend to be emphasized while pitches in between (around D natural and A flat) would be de-emphasized. But there is only one major key that includes both the notes B natural and F natural, namely C major — everything else has either B flat or F sharp. So if those two pitches are emphasized, it tends to impose a perception of C major. On the other hand the Serge Resonant Equalizer’s second and third lowest frequencies (the lowest seems to be anomalous) correspond to about B and B flat (or A sharp). These are present in both B major and F sharp major. However, the next frequencies correspond to A, G sharp, G, F sharp… There are no major keys with even just the first three of these, let alone all of them. Since they’re not repeating at octaves they’re not reinforcing the same notes in all octaves, and the notes being reinforced are spread across all major keys. So no perception of a particular key is being imposed. The idea is to create something akin to the fixed resonant frequencies, or formants, present in the human voice and in acoustic instruments. The formants add character to musical sounds. But normally these formants are not at any sort of regular intervals and certainly not at intervals that repeat in each octave. If a luthier, even one with no explicit knowledge of or ability to measure formants, were to make a guitar that had formants at B and F in every octave I think they’d listen to it, they’d say “No no no, that’s all wrong”, and they’d modify it to sound better — by adjusting the formants to be less regular. --- _[View the full topic](https://lookmumnocomputer.discourse.group/t/major-7th-interval-vs-octave-or-third-octave-interval/5903)._