The term 'PERFORMED AT ONE'S PEAK' can be answered with the 8-letter word 'YODELLED'. Yodelling is a form of singing that involves rapid and repeated changes of pitch between the low-pitch chest register and the high-pitch head register. It is a traditional form of singing that originated in the Alps, and is still popular in many parts of Europe and North America. Yodelling is often used to express joy or excitement, and is usually PERFORMED AT ONE's PEAK.