''Live'' singing to persons with dementia (PWDs) may be an underused but highly accessible resource for their caregivers, regardless of qualifications. A systematic literature review sought to illuminate who sings to PWDs, and with what objectives and effects, to address the question of whether it is the singer or the singing which is effective. The literature revealed that music therapists seek to address cognitive, behavioral, physiological, and social factors through one-to-one singing, whereas other caregivers are more broadly concerned with quality of life, often through facilitating activities of daily living. All included studies concurred that individual singing to PWDs can be effective in a variety of ways, depending on contexts and goals. PWD's perceptions of situations may influence the effectiveness of singing interventions. Music therapists are urged to empower professional caregivers to sing sensitively to PWDs during caregiving activities.