I was not aware people were using mobile phone apps for live performances (or any serious music production actually). Laptops are common, but using an actual iPhone for a live performance seems unusual. Is this really a common thing? Unless you are referring to playing music during a party or something? I guess I'm out of touch, lol.
iOS is incredible with its amount of music making apps, and I'm not talking about mixing existing songs. There are synthesizers of many different types (sampler, rompler, additive, subtractive, FM, granular), traditional samplers, loopers, drum machines, live input, etc.
That's cool. I guess there's no reason why things wouldn't naturally progress towards that. Phones are now powerful enough.
My only experience with creating music electronically was with Fruity Loops back in the day, so that's what I had in my head. I figured it would be hard to manipulate something like that on such a small screen.
The iPad does seem more suited, as the other comment mentioned.
I use Magellan with my iPad as it is cheaper than buying a Nord. Interestingly I can use Beyerdynamic headphones with my iPad, whilst having a USB keyboard plugged into it. This will not be possible with this iPhone.