In article
,
Jenn wrote:

http://www.britannica.com/eb/article...stortion&ct=eb

Another term sometimes applied to these standing waves is overtones. The
second harmonic is the first overtone, the third harmonic is the second
overtone, and so forth. ³Overtone² is a term generally applied to any
higher-frequency standing wave, whereas the term harmonic is reserved
for those cases in which the frequencies of the overtones are integral
multiplesŠ

End quote.

Yep, we use the terms overtones and harmonics interchangeably; the
numbers are just different.

Octave doubling is easy to hear in underpowered bass amps.

The listener's perception can reduce the separate pitch components into
a single sensation of timbre. This is a commonplace for conductors,
organists and players of chording instruments.

Stephen