Use Macbook Pro's single audio jack for both input and output at the same time? Basically, the Macbook Pro 13inch (early 2011) has only one audio jack, but I need two.

What I want to do is to plug in my electric piano (I have a male-to-male audio cable, I plug one end into the piano, the other in the microphone jack) into the computer, then play some backing track on the computer, and finally plug in headphones into the computer so that I can listen both to what I'm playing and the backing track.

This worked perfectly fine when I used my netbook. However, now I would like to use my macbook, but it has only one jack, so I can't plug both the piano and the headphones in.

Is there some kind of a splitter I could use so that I can plug in both at the same time? I found some threads online, such as this one, but some of the posts seem contradictory, so I thought I'd post here.

I would also welcome any answers that could explain the rationale Apple used for not including a second jack. Please do not use size as an argument; 10 inch netbooks fit 2 jacks just fine.

Thanks!
Yes - the good splitters mix the pins correctly to provide mono microphone and stereo output in the same jack. You can of course get breakout boxes like the Griffin iMic and have the benefit of a cleaner D/A circuit at the expense of carrying another device that's plugged into USB. Just like everything - some of the expensive products are over priced and some of the cheap ones are worthless. I'd go with a name brand - especially if their products are carried on the Apple Online or stocked in the retail stores.

Lion does add a control where you can select the speaker icon in the menu and switch from input and output.



As to the rationale - unless an engineer from Apple steps up, we'll have to speculate.

Here are the reasons to have fewer ports. (They're not al good, but they are reasons)


Simplicity - the iPhone / iPad / iPod touch all have one port. Many people don't need or want the confusion of knowing which port they plugged in to their mac. Just as you really appreciate having two, many appreciate having only one stereo jack.
Internal simplicity - one less switch, one less moving part, several solder points.
Internal spacing is far more important than external space. If you look at iFixit's excellent take apart manual - you will see there actually isn't room on the logic board for another connector. The design would have to sacrifice an USB port or the SD card slot to make room for a second package without reducing the space for the battery. These macs are packed incredibly tightly and despite the clean appearance of excess external space, inside they are packed like proverbial sardines in a can.


This lack of space likely cuts features from the smaller macs like a redundant mini headphone port.