|Arturia Mini with IAA transport shown|
With iPad's iOS7, one of the more significant additions is inter-app audio. We've had Audiobus for quite awhile now but inter-app audio makes audio sharing more integral to the operating system (Apple is allowed to make use of all the internal routines - unlike 3rd parties - gives them a bit of an unfair advantage, but I digress).
At this time, only a handful of apps support IAA but more are adding it everyday and it will become increasingly common in the coming months. IAA makes synths on the iPad act much more like VST or AU plugins do on the desktop. You can easily plug-in compatible synths to any DAW that supports it and record right from the synth into the DAW without Audiobus routing or the need for other apps running (this means a lot on the limited memory/cpu of the iPad!).
Two DAWs that already support IAA are Auria and Apple's Garageband. In the case of Auria, you simply plug-in the synth like you would any of its insert effects. For garageband, you select an IAA track type directly. Both work reasonably well at this point and not too surprising, there are occasional bugs in both too. It will probably take a few patches/releases to get things completely stable, but IAA is already very usable.
Auria is becoming my favorite DAW lately due to its fantastic automation and effects bus but it is a bit pricey. One nice development is that if you have any of the Sugarbyte effects (Turnado, Wow) for the iPad, you don't have to pay twice to use them in Auria. It recognizes them and lets you use them as native plugins - Auria native plugins do work better than IAA provided you are using Auria.
Garageband has many great additions in the iOS7 release - the track limit is up to 16 on older iPads and 32 on the brand new ones - I think there is a purchase in my not too distant future. Another more hidden but significant feature in Garageband for iPad is that for the first time, you can easily transfer lossless mix downs out of Garageband. Garageband used to be the "roach motel" of DAWs - you could get sounds in but couldn't get them out. Now you can mix down and select "Open with" to open the mixed down AIFF in another app. Not all apps support "open in", but one significant one that is is AudioShare which in turn lets you copy/paste anywhere you wish - so for the first time, Garageband plays well with others.
The piece below was created in Auria with only Inter-app audio synths. I used the Arturia Oberheim SEM synth for the arpeggios, Waldorf's Nave for some of the leads and the Arturia Mini for the bass. There were a few crashes but the entire thing was driven from within Auria and mixed/mastered and posted. I think this will be a huge development for iPad music moving forward!
Just an aside, the Arturia synths are available on desktop for roughly $100 each - on the iPad, they are $9.99 and sound extremely close to the desktop versions!