This cluster randomized controlled trial provides evidence that focused musicalinstrumental practice, in comparison to traditional sensitization to music, provokesmultiple transfer effects in the cognitive and sensorimotor domain. Over the last 2 yearsof primary school (10–12 years old), 69 children received group music instruction byprofessional musicians twice a week as part of the regular school curriculum. Theintervention group learned to play string instruments, whereas the control group (i.e.,peers in parallel classes) was sensitized to music via listening, theory and some practice.Broad benefits manifested in the intervention group as compared to the control groupfor working memory, attention, processing speed, cognitive flexibility, matrix reasoning,sensorimotor hand function, and bimanual coordination Apparently, learning to play acomplex instrument in a dynamic group setting impacts development much strongerthan classical sensitization to music. Our results therefore highlight the added value ofintensive musical instrumental training in a group setting within the school curriculum.These results encourage general implementation of such training in public primaryschools, thus better preparing children for secondary school and for daily living activities.