Composers ask for the hollow harmonic tone colour by putting a small circle above the sounding note, as in the fingering chart below. The most often used, and easily played harmonics (A5–C6), involve fingering the notes C-sharp4, D4, and E-flat4, with the second octave key, causing the note an octave and a fifth above to sound. If the harmonic does not speak easily, try putting more reed in the mouth and/or changing the embouchure pressure.
These harmonic notes can be very stable, yet are tonally quite different from the characteristic sound of the regular fingering. They are generally used only either as a specific effect, or when particular softness and pitch stability are needed. Harmonics also require less embouchure support, and may be useful when the embouchure has become tired. Alternating between the harmonic and regular fingerings of these notes helps find the center of the pitch on the more flexible regular fingering.
Colour fingerings involve adding keys, or changing fingerings to create tonal and slight pitch variations. One of the most famous pieces involving colour fingerings is the Sequenza VII by Luciano Berio, which calls for five different fingerings for a B4.
Some colour fingerings are fairly standard, and used by many oboists to stabilize pitch, and others are developed by each player to suit their instrument and reed set up. Resources such as the book Oboe Unbound give multiple fingering options. Colour fingerings are not meant to take the place of developing overall round, focused tone, but can help to stabilize pitch in certain situations, as well as creating different tone colours as needed.
Some of the more standard colour and pitch stabilizing fingerings include:
- adding the Low B key to stabilize F-sharp5
- putting some or all of the fingers of the right hand down, with or without the C4 key on C5 and C6 to darken and round the sound
- adding the C4 key on B-flat5, B5 and C6 to stabilize the pitch, particularly on the English horn
- adding the middle finger right hand to lower and darken A4
- covering the half hole more on D-flat5 to darken and cover that note
- adding the left F key on G4 (and on F-sharp5 on the EH) to sharpen it