Ok, so I like to record music pretty often and I normally use various layers, so I need to hear what I previously recorded on another layer in order to record the new layer. Before I had my Macbook (unibody 2009) I used to use headphones while I recorded the new layer so that the sound of the old layer wouldn't interfere with the new one. However, the new Macbooks only come with one audio input/output thing, and I can't use headphones while also having plugged in another device through the audio input. I thought about using one of those things that converts one input into two inputs, but I'm not sure if that will only give me 2 in's or 2 out's, or if it will actually work as one in and one out. I don't know if this is very clear, basically I need to get an audio in and an audio out at the same time. Suggestions?