Engagement with music is complex, influenced by music training and capacity, affective style, music preferences, and motivations.  Methods to assess music engagement have included auditory tests, psychometric questionnaires and experience sampling methods.  Limitations of previous research however, include: an absence of a comprehensive measure that assesses multiple aspects of music engagement; limited evidence of psychometric properties; and a bias towards equating ‘engagement’ with formal music training, overlooking other forms of strong music engagement.  In this paper, we describe a newly developed and psychometrically tested modular instrument which assesses a diverse set of music engagement constructs.  The MUSEBAQ can be administered in full, or by module as relevant for specific purposes.  In 3 separate studies, evidence was obtained from over 3000 adults (aged 18-87; 40% males) for its structure, validity and reliability.  Module 1 (Musicianship) provides a brief assessment of formal and informal music knowledge and practice.  Module 2 (Musical Capacity) measures emotional music sensitivity (α=.90), listening sophistication (α=.76), indifference to music (α=.59), music memory and imagery (α =.81) and personal commitment to music (α=.80).  Module 3 (Music Preferences) classifies preferences into six broad genres - rock or metal, classical, pop or easy listening, jazz, blues, country or folk, rap or hip/hop, dance or electronica.  Online administration uses adaptive reasoning to selectively expand sub-genres, while minimizing time demands.  Module 4 (Reasons for Music Use) assesses seven motivations for using music; musical transcendence (α=.90), emotion regulation (α=.94), social, music identity and expression (α=.90), background (α=.80), attention regulation (α=.69), and physical (α=.71).  The comprehensiveness, yet flexibility, of the MUSEBAQ makes it an ideal questionnaire to use in research requiring a robust measure of music engagement.