Squillo
Squillo is the resonant, trumpet-like sound in the voices of opera singers. It is also commonly called "singer's formant", "ring", "ping", "core", and other terms. Squillo enables an essentially lyric tone to be heard over thick orchestrations. Achieving a proper amount of squillo in any performing context is imperative: too much and the tone veers towards the shrill; too little and the purpose of the squillo cannot be achieved.
Squillo is recognizable by a distinctive brilliant, ringing quality in the timbre of the voice. This perception is caused by the presence of a peak in the 2–5 kHz frequency range, to which the human ear is particularly sensitive. The amplification of these particular harmonics is believed to be a result of a narrowing of the aryepiglottic fold just above the larynx. Voices with naturally acquired squillo are especially prized in opera because they allow a singer to sustain lyric qualities such as limpid high notes and consistency of tone throughout the vocal range, even in dramatic singing.
Uses of the squillo include:
- projecting a small timbre e.g. Tito Schipa, Bidu Sayao
- underscoring a dramatically important passage e.g. No, non voglio morir in Sola, perduta abbandonata from Puccini's Manon Lescaut
- singing through a thickly textured orchestration, e.g. the final bars of Libera me from Verdi's Requiem, in which a soprano has to compete against a tutti orchestra and full chorus
- supporting a pianissimo note floated over an orchestra e.g. Montserrat Caballé, Renata Tebaldi, Maria Caniglia, Cristina Deutekom
- supporting a long trill
- simulating a scream without compromising the timbre, especially in a verismic opera
- giving an impression of 'youth' to an aged voice, mainly via a cultivation of the head register