BVA (British Voice Association) (choice for voice)
London, UK, August 2008
‘A study of extreme singing vocal effects including distortion, rattle, growling and grunting’ Julian McGlashan, Cathrine Sadolin

A study of extreme singing vocal effects including distortion, rattle, growling and grunting

Julian McGlashan MD Queen’s Medical Centre Campus, Nottingham University Hospitals, Nottingham, UK
Cathrine Sadolin Complete Vocal Institute, Copenhagen, Denmark

Many rock, pop and heavy metal singers use vocal effects to enhance their singing style. A vocal effect is a vocal sound not connected to melody or test which is used to convey emotion, the mood of a song or to characterise a singer’s expressive style. Some of the more extreme effects have been termed Distortion, Rattle, Growling and Grunting.  Distortion is a grating noise that can be added to a note in any vocal mode. It is used frequently in rock/pop styles by artists such as Phil Lynott (Thin Lizzy), David Bowie and Janis Joplin.  Rattle is a ‘wetter’, coarser form of distortion used by singers such as Joe Cocker, Ian Dury and Percy Sledge.  Growl is a deeper, rougher noise used in traditional jazz and Death Metal styles of singing.  Louis Armstrong, James Brown, Johnny Winter and Whitney Houston use or have used this effect.  Grunting is a darker, more hollow form of growling effect giving a powerful demonic sound and is used in more extreme forms of Heavy Metal. Some of these sounds can sound harmful to the voice but many artists can produce them repeatedly on concert tours, for several hours per day, without apparent ill effects.

The Complete Vocal Technique (CVT) has been devised as a method of teaching singing which involves adding in specific vocal effects to a sound on top of vocal modes in a safe and controlled manner. The aim of this study was to examine singers trained in this technique using videostroboscopy and the Larngograph to firstly see whether there were identifiable patterns of laryngeal vibration and secondly see whether there was any evidence of vocal fold trauma.

Twenty (10 male and 10 female) singers aged 20-52 (Median 34) years old who had between 2 and 26 (Median 13.5) years of experience in the CVT were recruited.  They underwent a series of vocal exercises which involved attempting to perform these vocal effects in different modes (neutral, curbing, overdrive and belting) where possible.  Each subject was consented for the procedure.  Topical anaesthesia (cophenylocaine) was sprayed into the most patent nasal cavity. A 3.2 mm Olympus ENF V2 videoendoscope was used attached to OTV-S7 camera system. The endoscope was attached to the Laryngostrobe light source to record the laryngeal images in stroboscopic light so that the virating structures could be identified.  Surface grounded electrodes were placed on either side of the neck over the thyroid alar to record the Laryngograph signal and tie clip microphone used to record the voice. The Laryngograph waveform was used to trigger the stroboscope.

Although each singer attempted to produce these effects not all were able to produce them (Table 1).  In addition because of the shaping of the vocal tract during the production of some of the sound qualities, it was difficult to obtain a view of the vocal folds and laryngeal inlet in all cases.


Distortion Rattle Growl Grunt
No. Recordings(m:f) 17(8:9) 5(2:3) 16(7:9) 11(6:5)
No. Recordings(m:f) 17(8:9) 5(2:3) 9(4:5) 3(2:1)

Distortion was produced in 16 subjects by apparent random vibration of the false cords.  In 5 subjects there was additional vibration of the cuneiform cartilage, in 1 case almost exclusively. One subject produced a sound which was more creak with constriction. The vocal folds were seen to vibrate periodically and this was supported by the regularity of the Laryngograph trace. Rattle (n=5) was produced by vibration of the cuneiforms or mucosa over the cartilages, either freely or against the epiglottis. Again there was evidence on endoscopy or from the Laryngograph of periodic vocal fold vibration.

Growling (n=9) was produced by antero-posterior narrowing of the supraglottic structures and quasiperiodic vibration of the aryepiglottic folds.  This was seen well in 2 subjects and inferred in 5 others as only brief glimpses of the tips of the aryepiglottic folds or cuneiform cartilages were seen.  There was possible additional vibration of the false cords.  There was no evidence of constriction or harmful vocal fold vibration. In Grunting (n=3) the whole of the supraglottis appeared to vibrate in a random manner in 2 cases. In the other this was predominantly the aryepiglottic folds.  There was also a large glottal gap with apparent laxity of the vocal folds.


Vocal effects are used widely in pop, rock, jazz and heavy metal styles of singing.  Some sound harmful to the voice and probably are if attention is not paid to technique.  This study demonstrates how some of these effects are produced and that they can be produced in a ‘healthy’ way by ensuring good breath support, avoiding unnecessary muscle tension in the vocal tract, neck and shoulders, keeping to a mode and being well practised in the production of the effect.