Table 3. Categories and behaviour expressions of engagement.

Categories	Behavioural expressions
Facial expressions	i.  Mouth and lip movement
	ii.  Eyebrows movement (e.g. closed their eyes or raise their eyebrow)
	iii.  Facial changes (e.g. neutral look, smile)
Bodily movement and verbal articulations	i.  Large and subtle bodily movement (e.g. Hands and feet taping, nodding, clapping, moving with music)
	ii.  Verbally responding (e.g. singing, talking, mouth mumbling)
	iii.  Interacting with instruments (touching the instrument, playing with the instruments, making music)
Attention and awareness of activity	i.  Attention to stimulus (musician, other participants) undistracted eye contact
	ii.  Playing an instrument
	iii.  Moving along with music
Emotional response	i.  Pleasure and enjoyment as indicated by smiles and a look of contentment
	ii.  At ease look (looks as if s/he was relaxed)
	iii.  Sad or anxious look (appear agitated, e.g., eyes down casted like in moment of unhappiness; tapping his/her fingers as in people who are anxious)