ABSTRACT: This paper begins by looking at musical aptitude. It identifies research that compared the musical aptitude of people with, and without, an intellectual disability, and investigations that assessed the musical aptitude of diagnostic subgroups from within the intellectual disability population (Down syndrome, musical savants, autistic spectrum disorder, Williams syndrome). This paper then goes on to consider research that examined how individuals with an intellectual disability responded to active (improvisation, and Music Activity Therapy) and receptive (contingent, contingent-interrupted, and non-contingent music) interventions. The studies are ordered according to therapeutic outcome, and it describes their method, and considers various issues that arose. The conclusion summarises the strengths and weaknesses of the experimental writing, and identifies agendas for music therapy research with this population. It argues that the experimental research should not be considered in isolation. Instead, it suggests, that along with the descriptive writing (discussed in part one of the review), the experimental writing is part of a body of work that captures both the richness of clinical experiences, and the cause-effect relationships underlying those experiences. Music therapists have always been convinced that the in- terventions they offered were of great value to individuals with an intellectual disability (Watson, 2002). Early pioneers of the music therapy profession, described their clinical work in journals and newsletters, and documented the social and cog- nitive, physical, and emotional and psychological outcomes. For example, Juliette Alvin, who is widely considered the mother of music therapy in Great Britain, summed up her own experiences working with people with an intellectual disabil- ity by asserting "we know that music is an essentially flexible means of communication which can work at every mental, emotional, and social level" (Alvin, 1975, p. 2). A strong tradition of descriptive and philosophical writing developed; it not only demonstrated the efficacy of music therapy as an intervention for individuals with an intellectual disability, but also identified clinical outcomes, and informed and advanced clinical practice. (This writing was discussed in detail in part one of this review of music and intellectual disability literature (1943-2006)). However, while acknowledging the important role descriptive and philosophical writing has played, and will continue to play, in understanding and developing the role of music in the treatment of intellectual disability, the Evidence Based Medicine (EBM) framework incorporated into healthcare practice in Australasia, the UK, and the United States, is challenging practitioners to provide experimental evidence demonstrating the merits of the interventions they are offering. This part of the review documents how they have risen to that challenge, and how they have evaluated their work with people who have an intellectual disability. This paper is divided into three sections. It begins by reviewing investigations that considered musical aptitude (n = 81). It then goes on to discuss literature that examines how people with an intellectual disability respond to active music therapy techniques (n = 71), and concludes by examining material that evaluates their response to receptive music therapy techniques (n = 112). (In receptive music therapy the client is a recipient of the music experience, as distinct from active music therapy when s/he is involved in music making (Grocke & Wigram, 2007)). Musical aptitude (1) Background Musical aptitude is innate sensitivity to the elements of music, and, alongside learning, it plays a part in musical ability: the general term used to describe the level of musical skill and understanding. The relationship between musical ability, aptitude, and learning has been argued within the nature-nurture debate (Sadie, 2001). …