Hi! There is only one scene where Mona truly sings acapella in PLL. She sings Gravity in "A Dark Ali" which can be found on YouTube. She has sung snippets of songs (in 3x03 during her time in Radley, 6x01 in the hole of the Dollhouse) and performed Jailhouse Rock in the musical episode. All of these can be found on YouTube in varying quality!