| Clue | Source | Date |
|---|---|---|
| Sound from a deep guitar | Newsday | 25 Feb 2021 |
| Bottom of a chord | Universal | 08 Feb 2019 |
| Bottom of a chord | ||
| Choral extreme | The Washington Post | 03 Feb 2018 |
| Choral extreme | LA Times Daily | 03 Feb 2018 |
| Choral extreme | ||
| Resonant barbershop sound | LA Times Daily | 25 Dec 2016 |
| Resonant barbershop sound | ||
| Deep do | ||
| Low do, e.g. | ||
| Lowest tone in a chord |