Tahrir Patterns and Acoustical Analysis of Tekyeh in a Professional Iranian Classical Singer

"Iranian classical singing," called "avaz" in Persian, contains the ornament called a tahrir which is composed of a chain of tekyehs. A tekyeh is a fundamental frequency gesture that quickly increases and then decreases. Performing artists produce different patterns of tahrir during their singing. The primary aim of the study was to determine and describe different tahrir patterns based on fundamental frequency and temporal measurements of tekyeh produced by a professional avaz singer.

A live unaccompanied recording was made of a professional avaz singer singing the popular song "Morghe Sahar" (Dawn Bird) with free meter. Tahrir patterns were determined through auditory and spectrographic examination of the recording. Quantitative measurements were determined to distinguish among the resulting patterns.

Four primary tahrir patterns were identified. These patterns were categorized based on (1) the number of tekyehs, (2) fundamental frequency extent from the baseline to the tekyeh peak, (3) inter tekyeh interval duration, (4) tekyeh rate, and (5) tekyeh speed quotient. Pattern 1 consists of one tekyeh and is called a "zinat." Pattern 2 is a multiple tekyeh gesture with relatively long plateau intervals. Pattern 3 is a multiple tekyeh gesture with relatively short plateau intervals. Vibrato-like Pattern 4 is also a multiple tekyeh pattern with short plateau intervals like Pattern 3 but with relatively small frequency extents.

Four uniquely distinguished tahrir patterns, defined via acoustical analysis and the number of tekyehs, were identified using visual and auditory inspection of the various tahrirs produced by the participant. For the singer, Patterns 1, 3, and 4 constituted 96% of all the tokens. None of the tekyehs produced by the participant studied here appeared to switch between vocal registers between the lower and upper notes. The results have ethnomusicological, physiological, acoustic, and pedagogical importance for Iranian classical singing.