# The missing fundamental

Play a note through a filter that removes its lowest harmonic and keeps harmonics 2 to 6. You might expect the pitch to jump up, but it does not: you still hear the original low note. The brain recognises the pattern of the harmonics, 2, 3, 4, 5 and 6 times the same frequency, and hears that frequency as the pitch, even though nothing is sounding there. This is why a small phone speaker, which cannot produce low frequencies, still lets you follow a bass line.

Connects to:
- [The cochlea](https://mapideas.org/i/mu_cochlea)
- [The harmonic series](https://mapideas.org/i/mu_harmonics)

Sources:
- [Wikipedia: Missing fundamental](https://en.wikipedia.org/wiki/Missing_fundamental)
- [What is music? Module 1, Lab 1 missing-fundamental buttons](https://sofiagallego.com/what-is-music/)

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