Hi Andrew, Building a PC is a Doddle. get onto your favourite PC Parts Supplier and go window shopping.
http://www.cplonline.com.au/
http://www.gigabyte.com/
You'll need
1. Case, they don't always come with a PSU(power Supply)
1. PSU
1. Motherboard.
1. CPU Intel or AMD dependant on your M/B. make sure it is compatible
2 or 4 Ram Chips. go to at least 8Gb
1 DVDRW drive
1 or more HDD
1. Graphics Card. If your only doing music then don't go overboard with the graphics. something with 1-2Gb Ram
1. tube silver silicone
100. Patience.
Install M/B into care and screw down in at least two places, If the case doesn't have plastic standoffs this may be screw down in as many places as the case has.
Ground yourself to the case, then Install CPU into socket taking care to orient the CPU with the markings.
Squirt a dob of silver silcone onto the top of the CPU about the size of a 5cent piece.
gently place the CPU cooler on top of the CPU, the press down and secure with whatever clips or screws that are proviced for the CPU Cooler.
Insert Ram into sockets and secure the end clips.
Install the graphics card on the M/B
Install DVDRW into case(this can be done before the M/B
Install HDD.
Connect up all the Power, Sata cables, front of Cabinmet cables.
You should be just about ready to pug it in and power it up.
PK