Table 2 Overarching themes and sub-themes

1. Activity mechanisms

S1.1 ‘Authentic’ musical engagement

S1.2 New singing skills

S1.3 Singing outside of class

P1.1 Varied play activities

P1.2 New play ideas

P1.3 Playing outside of class

2.Psycho-emotional mechanisms

S2.1 Singing feels good

S2.2 Singing time for mums

S2.3 Singing as immersive

S2.4 Singing as achievement and purpose

S2.5 Singing supports bonding

P2.1 Play feels good

3. Social mechanisms

S3.1 Singing impact on babies (calming)

S3.2 Singing as part of group

S3.3 Singing supports routine

P3.1 Playing as part of group

P3.2 Play supports routine

P3.3 Play impact on babies

4. Environmental mechanisms

S4.1 Calm and inclusive singing environment

S4.2 Importance of singing leader

P4.1 Calm and inclusive play environment

P4.2 Importance of play leader