For this post, I want to share my responses to a recent email.  Don L. asked some great questions about equipment for Mainstage, similar to what many others have asked.  Here you go!

I am new to MainStage and would like to use MainStage for my church’s live worship. What equipment do I need?

If you want to play keyboard sounds through Mainstage, you just need Mainstage software from the App Store and a keyboard that can connect to a Mac. Newer keyboards can usually connect directly through a USB cable.

Older keyboards will require a MIDI interface (I recommend this one). Connect a MIDI cable from the keyboard, then to the MIDI interface, which then connects to the computer via USB.

I was doing some research and some recommended using a Mac Mini. Why?
I really can’t say why someone would prefer a Mac mini.  Any Mac made within the last 3-4 years or so (at least) will work. I’ve even seen it work well on a Mac made in 2007.  Most people find the laptops to be convenient.    I use a Macbook Air with a 1.4 GHz Intel Core i5 processor and 8GB of memory.  More processor speed and memory will enable you to play with lower latency.

Do I need to purchase an audio interface? If so, what is a good one for my purpose?  I see other musicians using the Apogee Duet.
You do not necessarily need an audio interface; the headphone jack can work. For sending audio to a mixer, I like to step up to at least a minimal interface, like this one. It will give a little cleaner output than the headphone jack.

Sound quality is a matter of need vs. cost. Yes, a Duet will sound better than the headphone output, but it also costs $565 more.   You may not even be able to tell the difference between the Apogee and the Behringer in a live environment, depending on the quality of other gear in the signal chain.  (Now in a studio environment, the difference is pretty obvious.)   You’ll have to judge what level of cost vs. quality is appropriate for your situation.

If you have questions about Mainstage, feel free to contact me.
Grace and peace!/Peter