## 1 Introduction  
### The Burden of Dementia and Non-Pharmacological Approaches as a Research Priority  
The proportion of older adults is estimated to double from about 12% to 22% between 2015 and 2050 [1], which will increase the number of age-associated diseases, such as dementia, which already presents 10 million new cases every year [2]. Dementia is a clinical syndrome characterized by a progressive and irreversible deterioration of cognitive functioning, leading to cognitive impairment [3]. Consequently, emotional and behavioral domains are also affected, resulting in a progressive loss of functional abilities and autonomy [3, 4, 5].  
In recent years, investigation of the consequences of cognitive deficits has grown, and ways to reduce the impact of both healthy and pathological age-related cognitive deficits are considered a research priority [3, 4]. Even though pharmacological approaches are the first line of treatment for cognitive and behavioral symptoms, their effect is still limited to the early months of treatment [4]. Increasing evidence supports that non-pharmacological approaches (e.g., cognitive and psychosocial interventions), developed to be implemented in parallel with the former, can (1) maintain and improve cognition, (2) encourage social interaction, and (3) enhance the well-being of IwD [5, 6]. However, there is still a need for investment in these approaches (e.g., positive approaches such as reminiscence, validation therapy, and reality orientation) to complement the medical and neurological models [7].  
The most studied and well-established non-pharmacological intervention for individuals with mild to moderate dementia is Cognitive Stimulation Therapy (CST) [8, 9]. The CST program is an evidence-based approach developed by [PERSON] and colleagues [10, 11] which builds on the significant impact of reality orientation, reminiscence, and validation therapy. The underlying assumptions behind CST are:IwD can benefit from cognitive stimulation if we mobilize relatively preserved cognitive functions (e.g., crystallized abilities such as semantic memory and verbal skills);
2. Even in advanced age, exposure to enriched environments (i.e., those that are socially, and cognitively challenging) can enhance cognitive reserve and neuroplasticity [12; 13].  
Concerning point 1, it is known that even in moderate to advanced stages of dementia, musical memory is one of the abilities that remain relatively intact [14]. It is hypothesized that music-processing abilities precede the development of lexical language functions. This hypothesis is corroborated by findings which demonstrate that IwD are still responsive to music even when unable to communicate verbally or recognize words. For instance, it has been shown that individualized music listening can lower depression symptomatology and agitation in IwD and can increase positive emotions [15].  
Additionally, music is frequently associated with life experiences [16]. When studying musical memory in [PERSON]'s disease, [PERSON] and [PERSON] found that memories associated with specific music would be recollected longer than memories with no association with music [14]. This suggests that using music as a reminiscence element in cognitive stimulation programs can positively affect cognition [17]. Regarding point 2, it is of the utmost importance to enrich the environment for IwD. Here, combining both music and reminiscence-related elements, as well as customized cognitive stimulation programs, could impact cognitive reserve and neuroplasticity. However, there is a need to find frameworks that facilitate the combination of such elements, allowing the replication and customization of cognitive stimulation activities.