A nigun or niggun is a form of Ashkenazi Jewish vocal music sung in group settings. Nigunim are melodic tunes, often using repetitive non-lexical vocables such as "bim-bim-bam", "lai-lai-lai", "yai-yai-yai", or "ai-ai-ai" rather than with formal lyrics. Sometimes, a nigun is expressed as a mystical musical form of Jewish prayer or glossolalia. Hebrew Biblical verses or quotes from other classical Jewish texts are sometimes sung repetitively to form a nigun. Some nigunim are sung as prayers of lament, while others may be joyous or victorious in theme.