Loneliness is common in both persons living with dementia and their informal caregivers, and a factor negatively affecting disease progression, health and wellbeing. However, intervention studies to address loneliness show inconsistent effects. This study aims to evaluate effect of a community-based group intervention - music therapy informed dementia choirs - on loneliness for home-dwelling people with dementia and their informal caregivers. We will recruit participants to five dementia choirs with 15-20 people in each and implement a crossover study with measures collected at four timepoints: baseline, 12-week follow up, 22-week follow-up after an extended summer holiday, and 12-week follow-up after the summer holiday. The primary outcome, loneliness in participants living with dementia, will be measured using the De Jong Gierveld loneliness scale. Secondary outcomes will be depression, experience of meaning in life, apathy and mood for the participants living with dementia, and loneliness and caregiver burden for the informal caregivers. Cognition in the participants living with dementia, measured with the RUDAS assessment tool, will be included as a control variable. Further, measurements to evaluate the cost effectiveness of the choir intervention will be included, and qualitative data collected through semi-structured interviews to explore the experiences and possible impacts of the choir intervention in the participants' lives.