This is a topic that comes up from time to time with me mainly because we see so many actors from Shortland Street either appear in a music video or even in a band. So this is where I will compile a list of these videos with a little bit of info on who to watch for.
But first up here is the first ever theme song for the series sung by Tina Cross 

https://www.youtube.com/watch?v=Vy5dD46WmEU (can be purchased here as an mp3 http://www.amplifier.co.nz/release/85950/shortland-street-theme-single.html?play=85952#item85952)

next up is a video from The Mutton Birds in this video we see actress Elizabeth Mcrae who played the character Marge Neilson https://www.youtube.com/watch?v=lceOrRb2zn8

Next up is an iconic track from Greg Johnson in the video appears Jo Davidson who played Gina Rossi 
https://www.youtube.com/watch?v=k4jzxQjGli0

we are still on the topic of Greg Johnson in this video for Come On we see Tandi Wright (she played Caroline Buxton) playing the angel in the video https://www.youtube.com/watch?v=b125ErDeR_Y

This time around it is a Greg Johnson song but performed by The Strawpeople which on this track atleast has Stephanie Tauevihi who playe character Donna Heka https://www.youtube.com/watch?v=7NT4hX9VNxI

Now before there was the Ferndale Strangler there was Jester for Johnny Barker (who played Joey Henderson who ended up being best known for being the Ferndale Strangler) here is my fave track from Jester https://www.youtube.com/watch?v=Y_Ngjcl1eDQ 
Funnily enough Johnny appeared on Shortland Street in 2000 and ended up being Waverlys boyfriend as seen in the 1st few seconds of this video performing the song from the previous mention https://www.youtube.com/watch?v=wj7RMa846jU

Next we have Annie Whittle who came to the attention of EMI in 1976 and in 2001 came to the attention of Ferndale as Barbara Hayward https://www.youtube.com/watch?v=EwLFhvJslew 


Now it seems those playing roles in the Hayward family have musical backrounds or atleast Masrhal Haywards actor Paul Reid who we became familiar with in Rubicon along with their catchy tune Bruce  https://www.youtube.com/watch?v=e91v1hC6__Y


Now next up this talented lady would best be known for her role as the face of House Of Travel s commercials Miss Lucy in Shortland Street sh played Nurse Christine Hastings in 1998. We also heard her in a few different musical forms over the years in Growler, under the name Marvey King and Sherlocks Daughter here is  how I discovered her https://www.youtube.com/watch?v=KlK8-_HJonE

One final note is in regards to Michael Galvins character Chris Warner over the many years it has been noted his affection towards the music of The Flying Nun Label one occasion for a talent quest he perofrmed Down In Splendor from Straitjacket Fits and at his wedding recption after marrying Rachel Mckenna we see The Chills perform.