Ah, DarkRed - foot in mouth again regarding hardware
Of course this can be done ITB. The main thing I notice is how clean, sonically, the track is - each sound has it's place in the spectrum, nothing is competing for space, balance is great. When you start with that, the final mix down is much easier.
So does Avicii, does that mean that most of his sound is achieved in software? No.
What we are hearing is mainly the result of hardware partly from what is in the original sounds fed into the FL studio project, partly the hardware added into the mix during mixing and partly the hardware engaged in mastering, the software has simply not eaten up the signal to the point that the beauty of the hardware is not present anymore and for that you need a certain very specific ITB setup and approach. The heavy duty work towards this sound is still happening in the hardware domain which is important to understand.
Hardware reverbs and delays fill out the sound stage like this when you don't let the software in the way of it. With software I mean your whole ITB configuration and setup including the hardware required to make it run.
When it comes to creating an ITB setup that actually works, this is a pretty advanced process, much more advanced than many think.
First of all, you need a system that is designed to do heavy processing in the user mode. A Macbook Pro + iOS based system is a good start. This system then needs to be optimized strictly for music use, which is a separate topic that divides into how to do so through the hardware configuration and how to do so through the software configuration. The audio interface, its integration with the system and the CPU is paramount here. The rest is then about how and when to engage this system as oppose to engaging additional hardware. But all of this is stuff that mainly just pros do, home recording engineers don't do this stuff properly (they are incredibly sloppy with this and do things just because it works), they just think whatever works or put in another way - they setup something that they can afford that connects OK and works to get some audio job done. That's not how njnichols did it.
But, essentially the difference in approach is really that pros achieve the quality early and they then ensure later processes don't get in the way of that. This is the thing that is so difficult to teach to kids and home recording people, they are so stuck and stubborn about their ITB mixing that they demand anything is possible. When Chris Lord Alge produces a hit mix, 95% of it is in the decision when he goes: yes I like this, this is ready for mixing, I know what to do with this. And when he says he knows what to do with it, it is true, he engages hardware when that is required and he engages software when that is required. That's the difference. A home recording engineer, takes whatever content thrown at him and engages his low performance ITB setup onto it. The result is therefore that.