The music box plays "HaTikvah", written and composed by Naftali Herz Imber. It is the Israeli national anthem.
In the 2nd Pub scene appearance of Phyllis (Celia Imrie ) and Ben (Clive Russell ) during the sign off musical scene of "Always Look On The Bright Side Of Life" you will see a couple dancing to the song on the TV behind them. Note - there are 3 total Pub scenes with Phyllis and Ben, of which 2 are during the sign off performance.
This is the very first time one of the kid actresses whistles.