NOTE: all the oboe sound samples were performed by Francesco Luglini on 26/10/2007. Sound engineer: Valerio Carboni.

Structure of the instrument

The oboe has a conical body with a slightly more pronounced flare near the bell of the instrument. Unlike the clarinet and the saxophone, the oboe has a double reed. Its mouthpiece in fact looks like a small piece of drinking straw flattened at the end, which is inserted into the player's mouth.

Oboe	"Exploded" view	Parts
Parts 1 and 2	Part 3	Part 4

How the sound is produced

• Unlike the single reed, in which a flexible blade oscillates against a fixed support (see clarinet), in the double reed both edges are flexible and oscillate against each other in phase opposition.
• The function of the reed, whether single or double, is in any case essentially the same: it turns the continuous air flow generated by the player into an oscillating flow, and hence into sound waves inside the resonating pipe.

The source of the oscillations

reed vibrating

When an air flow is made to pass through a narrow passage, by the principle of conservation of energy the pressure inside the passage decreases (Bernoulli's theorem), all the more the greater the air flow passing through it. When the walls of the passage are flexible, as in the double reed of the oboe, a decrease in pressure inside them can make them move closer to each other. As they move closer, however, the air inlet becomes smaller, reducing the flow. As the air flow decreases, the pressure inside the reed rises again, and the walls of the duct move apart again. This process repeats cyclically at a frequency that depends on the characteristics of the reed.

The formation of timbre

The source of the oscillations in the air pressure, that is, the reed, driven by the pressure of the breath and of the musician's lips, generates a complex excitation, approximately triangular (you can hear it in the sound sample of the reed). In other words, it is not a simple harmonic oscillator. This waveform is fed into the pipe of the instrument, and the pipe reshapes the weight of the individual harmonics, selecting those corresponding to its own resonance frequencies and suppressing or attenuating the others.

The timbre of the instrument is therefore produced by the combination of the wave generated by the reed and the characteristics of the pipe. In particular, the pipe has holes, which can be opened or closed by means of a complex system of keys. The main function of the holes is to shorten the effective length of the air column actually vibrating in the instrument, so as to produce notes of higher frequency than the one that would be produced using the whole length of the instrument (all holes closed).

Acoustic characteristics

Excerpts of live performance

A short passage from Così fan tutte by W. A. Mozart was recorded in an almost reverberation-free environment with a microphone very close to the instrument. The sample faithfully corresponds to what is heard at a short distance from the instrument, but does not reproduce the listening conditions of a concert hall. The sound is very faithful to the original, but very "dry". The right and left channels are identical copies of the same signal.

waveform	spectrogram	Audio
		OB_SampleDry.mp3 Oboe: from "Così fan tutte" by W. A. Mozart ("dry" version)

A basic electronic manipulation of the sample consists in introducing dynamic compression of the sound, that is, automatically reducing the difference between the loudest and the softest sounds, so as to even out its dynamics. Note that now the right and left channels show small differences. The net effect is to introduce a "virtual" listening environment, which simulates a slightly reverberant real environment, and therefore reproduces more faithfully the sound that would be heard in a concert hall. The sound seems richer overall, although all the pitches and durations of the notes are unchanged with respect to the "dry" sample.

waveform	spectrogram	Audio
		OB_SAMPLE.mp3 Oboe: from "Così fan tutte" by W. A. Mozart (version with dynamic compression)

The sound of the reed

The sound obtained from the reed alone resembles the one obtained by blowing into a drinking straw flattened at one end. It is a rather harsh sound, corresponding to an approximately triangular wave. The player can change the fundamental frequency of the emission by changing the position of the reed with respect to the mouth and by tightening the lips more or less. This amounts to changing the elastic constant of the vibrating system, and so the base frequency can only be raised, as illustrated in the example recorded here.

waveform	spectrogram	Audio
		OB_Ancia.mp3 Oboe: reed alone

Harmonics

The analysis of the spectrum of the oboe shows a characteristic maximum that does not coincide with the fundamental. The bright, slightly nasal timbre of the instrument is commonly attributed to this feature. The player can also force the instrument to pass from normal emission to a higher mode, corresponding, in our case, to the third harmonic partial. In some cases, however, as can be heard in the third example, the harmonic is activated during the attack of the sound and spoils a "clean" attack.

waveform	spectrogram	Audio
		OB_Sib.mp3 Oboe: passing from a full C4 to its third harmonic (G5) and back
waveform	spectrogram	Audio
		OB_Armonici.mp3 Oboe: passing from a full C4 to its third harmonic (G5) and back
		OB_AttaccoArmonico.mp3 Oboe: the resonance on the third harmonic spoils the "clean" attack of C4

Timbre and register

Here too we highlight the great change in timbre that occurs simply by playing the instrument in its low register rather than in its middle or high register. As already done for the other instruments, we compare the three spectra corresponding to the Cs of three different octaves, normalizing them in frequency and amplitude, that is, rescaling them so that they cover the same frequencies and the fundamental harmonic component has the same amplitude. It is evident that the spectra have completely different shapes; indeed, it is not at all obvious how the ear can attribute them to the same instrument.

spectrogram	normalized spectra	Audio
		OB_Ottave.mp3 Oboe: C in three different octaves

Special effects

On the oboe, "double" sounds can be produced by a suitable setting of the lips. They are sometimes perceived as "noisy", unstable sounds (first sample), and sometimes as the superposition of two distinct tones (second sample). To understand what is going on, we need to enlarge a portion of the spectrogram, increasing its frequency resolution. In the first case we see that each spectral "line" actually consists of eight widely distributed frequencies with decreasing intensity, in an interval of about 200 Hz around the main frequency (the first, most intense line is at about 387 Hz, which is also the frequency of the perceived sound). Actually only the first two side lines are particularly intense, and they lie within 40 Hz of the main peak. This spectrum corresponds to that of an amplitude modulation of the central note, but the bands are not wide enough to be resolved by our ear. Indeed, the corresponding sound seems to "vibrate". (On this subject, see the pages physiology of the auditory system and critical bands)

spectrogram
low frequency resolution	high frequency resolution
waveform	Audio
	OB_SuoniDoppi1.mp3 OB_SuoniDoppi1

In this second case, instead, the high-resolution spectrogram again shows a harmonic series of lines, flanked by only two sidebands at a distance of about 96 Hz from the main line. They are therefore far enough apart to be perceived as a superposition of distinct sounds. The first note is a D₆ at 1190 Hz, while the double sound seems to contain also an A₄ at 430 Hz.

spectrogram
low frequency resolution	high frequency resolution
waveform	Audio
	OB_SuoniDoppi2.mp3 OB_SuoniDoppi2

Vibrato

Vibrato on the oboe, as on almost all instruments, is a combination of frequency and amplitude modulation. From the diagrams below it can be seen that both modulations occur at a frequency of about 5 Hz. In amplitude there is an excursion of about 5 dB, while in frequency there is an excursion of about 15 Hz at the fundamental. As always, the higher harmonics undergo larger excursions.

waveform	spectrogram	Audio
		OB_Vibrato.mp3 Oboe: sustained note without and with vibrato

Dynamic range

The dynamic range, that is, the ratio between the power radiated by the instrument in fortissimo and in pianissimo, is around 12 dB, as can be seen from the logarithmic scale in the diagrams as a function of time.

waveform
spectrogram	Audio
	OB_PianoForte.mp3 Oboe: piano, forte

Musical features

Introduction

The oboe is, together with the bassoon, the instrument that has lent itself least of all to research on timbre and articulation, because of its mechanics and its peculiar double-reed mouthpiece; nevertheless it has such a characteristic colour that it is an indispensable element in the connotation of certain particular musical situations.

The classical and the popular in Ennio Morricone's approach

In the celebrated Gabriel’s theme, Morricone entrusts to the oboe the main melody of the film The Mission, in order to meet two needs, one formal and the other what I would call "musical semantics". In the first case, the director (and therefore the composer) needed a piece of intradiegetic music (the theme gives voice to the instrument that the protagonist builds in the film, an enchanting instrument, a symbol of peace and an invitation to brotherhood) to become extradiegetic (with the musical expansion and the involvement of the whole orchestra). The second reason is more strictly musical: the sequence played by the oboe has a free, almost improvisational character, and recalls certain stylistic features of Gregorian chant (it seems that the melody itself was conceived starting from one of these ancient chants); the timbre of an "archaizing" instrument was therefore needed, and the oboe, a double reed like the rustic zampogne and bagpipes, filled this difficult role well. Moreover, the melody ranges from the middle-low register, harder and harsher in timbre, to the high register, poorer in harmonics and therefore sweet, almost to the point of taking on a diaphanous colour.

The visionary quality of Gustav Mahler

To turn instead to an example from the symphonic repertoire, no instrument could better embody, in the third movement of G. Mahler's 1st symphony, the larmoyant, ironic and disenchanted tone that today reminds us of a band in a 1920s American nightclub. Here the composer exploits the markedly nasal timbre of the oboe, sensing its sly, winking, almost "ingratiating" but also somewhat nostalgic character. Of course, a thousand words are not enough to express what a short musical theme can convey.

Further reading and links

• We invite you to read the essential page Sound and resonance, where you will find the general principles of how a musical instrument works. Reading it will help you better appreciate the peculiarities of the instrument described on this page

• In our 2D Waves virtual laboratory you can experiment with the formation of reflected waves and their dependence on the shape of the pipe and on the position of the holes of the instrument. The page experiments on sound tubes describes some guided experiments.