recording podcasts (mac) do i need a mixer? any good software
 

i want to start recoridng podcasts and will have guests etc via skype and so on and i want to be able to record the conversation in an editing software in high quality

now would i need a mixer? i would like to play music / jingle / sfx in the background and also record myself speaking... rather then doing this post editing

is there a software which allows you have multiple channels to record ?
or should i invest in a basic mixer (any reccomendations)

also i have a macbook

many thanks