I need help from someone who knows a lot about setting up a computerized office phone system (music on hold)?

Hi.

I want to make this myself, because i like making things myself. Plus, i don't want to spend any money, because I like making things myself without spending money. Its ok if they get a little ghetto because that makes it more fun

So, what I want is to be able to have my land line phones (2 lines) to be connected to a computer which will run scripts that handle incoming calls. I want there to be music on hold when i put them on hold, and I want to be able to transfer the calls and stuff like that.

My question is: Will a phone modem card work to plug the phone line into my computer?? Like is there software that can use a modem??