Undertone or Undertones may refer to:

• Undertone series, a sequence of notes that results from inverting the intervals of the overtone series
• The Undertones, Northern Irish band
  • The Undertones (album), 1979 album by The Undertones
• Northwestern Undertones, a cappella group at Northwestern University, Evanston, Illinois, United States
• From woodwind instruments: Undertones may emerge as the tone component(s) of a note's sound which are lower in pitch than the frequency of the note.

Examples of woodwind undertones:

• • Every note above low-G on a GHB pipe chanter entails some undertone of low-G; the energy of the low-G undertone comes from the dual side-holes towards the bottom end of the pipe chanter.
  • Much more rarely considered is the sound - as undertone - which emerges from the very bottom of the chanter and might be termed: horntone, horn-note, belltone, or - most politely and concisely - the bellnote.
  • The practical (conventional) fingering of notes entails further undertones such as: low-A emerging with fingered E, and C(#) & B undertones but not low-A with fingered D.

Relevance: Ill-tuned lower notes may - as undertones - mess-up the practical sound (tuning) of higher notes.

Separate pipes of a pipe organ, or of a GHB versus the pipe chanter - that is the drones - should not be practically discussed as undertones; they can be turned on and turned off, so each separate pipe is considered to produce its' own sound(s).

• Operation Undertone, part of the Allied invasion of Germany in World War II
• Undertone (advertising company), a New York-based digital advertising company
• An underlying or implied tendency or meaning; a subtext
• Skin undertone, as it applies to cosmetics; see color analysis (art)

• Overtones (disambiguation)