Some background for my question: So, as many of you know, the new "late 2008" macbooks and macbook pros have a "hidden" microphone-level input in addition to the traditional line-level input. The microphone input is inside the headphone jack and uses the iPhone-style plug (with three connections or poles on the minijack plug). For example, you can plug in the new in-ear headphones with the microphone to the MBP and utilize the plugged microphone on the MBP. In the Sound Preferences you can see the input source switch from "Internal Microphone" to "External Microphone" as you plug in such a headset. The question: I would like to plug in a traditional microphone and/or a guitar input. These are microphone-level inputs. However, does anyone have any idea how I could utilize the microphone input inside the headphone jack on my late-2008 MBP? I can imagine an adapter that would make this conversion --- quite a simple adapter. I could buy the cheapest iPhone headset with a mic and cut off the headphones, purchase a 1/4" jack from RadioShack, and do some soldering. But, this will result in an expensive, time-consuming, jerry-rigged solution. Does anyone know of any such adapters that can go from a standard 1/4" or 1/8" jack to a iPhone-style 1/8" mini plug (that connects the signal of the jack to the microphone pole of the plug)? This would be especially useful with the new version of GarageBand '09 that allows you to apply effects to a plugged-in guitar.