I'm interested in recording some of my practice sessions mainly for the purposes of critiquing my bass lines against recorded tracks (these can be existing songs, music coming from the irealpro app), etc...

I'm not really a technophobe or luddite, but I do want this to be as painless and as little work as possible (main reason for that is I deal with enough technology at my day job, so I want to deal with as little as possible at home).

The audio source would be my iPhone as that's where most of my music resides in the form of my own personal library, various music training apps, and Apple music.  While my own personal library does exist on some other computer, Im not interested in going through the trouble of importing tunes into the laptop computer I'd be using for this.  All of that music is on my phone so thats the easiest way for me to deal with it.

Bass signal would more than likely come from the DI out of one my amps..

Given all this, what's the best way to accomplish what i want to do?  inexpensive portable mixer like Soundcraft 8 channel?  This has RCA jacks for an input so that solves the problem for input from my phone...Or do i really just want to buck up and get something like a Focusrite Scarlet?  Problem with this is I don't see an input for auxiliary audio from an iPhone.

IK Multimedia iRig, and Amplitube 4 for your iPhone.

Let me highly recommend PowerTracks from PGMusic.com.  These are the same fine folks
that bring us "Band-in-a-Box".

https://www.pgmusic.com/powertracks.htm

https://www.pgmusic.com/powertracks.features.htm

PowerTracks is a virtual 48 track recording desk on your computer.  Each track is stereo, and
you can pan left to right, EQ, copy and past.

For example, one track has a little problem in the 3rd verse, but that part is identical to the
same instrument in the 2nd verse.  You can copy/paste that part of the 2nd verse over to the
same spot in the 3rd verse, patching over it.

I had a tune I had written for saxophone quartet with my notation program.  I exported it as a
Type 1 midi file, which each instrument is a separte part of the midi.  I dropped that midi file
into PowerTracks and it filled in tracks 1-4 in PowerTracks.

With headphones, I muted track one, but could hear tracks 2-4 via headphones, and played
along with it, recording myself into track 5.  Then I muted 1 and 2, listening to myself on
track 5, and midi on tracks 3 and 4... recording myself on track 6.  Repeated this process
until I had tracks 5-8 recorded by me.  Once that was done, I deleted tracks 1-4.

Then a few minutes panning each of the four tracks 5-8 to place each instrument where I
wanted on the "sound stage".  EQ applied to each channel as needed.  Then mixed it all
down to stereo onto channel 1.

After that I applied echo and reverb tastefully, and done!

The same thing can be done adding your vocal or instrumental lead to backing tracks you
did with Band-in-a-Box (it's at PGMusic, read up on it).

This is all on your computer, laptop or PC.   It's much more than you can do on your phone.

If I were to recommend a DAW, I'd recommend Reaper. It's free to try with an unlimited demo (they only ask you to pay the $60 on the honor system). It's not limited on haw many tracks you can use. You can cut,copy and paste just like you can with any DAW. It comes with a host of plugins, and supports all plugin types. Plus setting up sub mixes/groups is as easy as drag and drop.
reaper.fm

But all of that said, if he has a Mac, Apple has Garage Band for free. It's also a good DAW.

ETA: And if he's going to go the computer/DAW route, he's gonna need a decent interface. I recommend a Focusrite Scarlett 2i4. Alot of bang for the buck and sounds pretty good for be to ng as cheap as it is.

***but***

He wants the easiest and simplest. And that would be an iRig for his phone.

So its been a week or so since I posted this...update time.

First, as to the irig, i tried one last year....first one was D.O.A. out of the box, i had the second one for about a week before that went back.  I was basically completely unimpressed with the quality/cost ratio, and the sound was not very good either.  Plus, unless I am missing something with the rig software you cannot have a tune playing in the background from the apple music player while irig is going, and recording my own bass lines over previously recorded tracks or stuff playing from irealpro or drum genius is what I am interested in doing.

Last week i had a sound craft notepad8fx delivered...It more or less did what i wanted it to, it allowed me to play stuff streaming from my iPhone while i laid down bass tracks.  I could not get this to work with reaper, at all.  Signal levels were way low and when I raised the signal level i got this strange sine wave type feedback.  It did work ok in garage band though.  However this was still a little more complicated and messy than i wanted.  MBP, mixer, all the cables just resulted in more of a mess than i wanted to deal with.

I was really trying not to spend a lot of money on this project, but in the end just said screw it and bought a Zoom H6.  Small footprint is perfect.  I can use the line in on the mic to record audio from my phone, and lay down bass tracks that way and than listen back on headphones without having to transfer to a computer.  Sound quality is fairly decent also.

Awesome, I'm glad you found something that works.

Glad you found a solution OP. I take an even lazier and cheaper route. I have a speaker which I plug my phone into and set my phone on my music stand with the front facing camera on. Put on a backing track, hit record and jam.

No it doesn’t sound great but it’s honestly not horrible. The speaker is of good quality so the backing track sounds good. It’s just for me to see or to send a friend a quick riff or part so it works.

Now if I was trying to post the vids for all to see, hell no.

Tag for interest.

I love this thing. Nice built in mic, + 2 inputs with 48v available. You can only use 2 channels at one time. Easier to use that the old Tascam cassette port-studios.

Its an Izotope Spire Studio if you don't want to click the link.

I have a few other devices, but this one will load directly to your phone and/or store the tracks on itself. It has a battery, and can be used with or without the phone interface. It has a couple of amp sims built in also that aren't bad. The mixer interface is really cool to.

I also have an Apogee Duet that will do 2 tracks simultaneously, and an X-32 that will do 32 tracks simultaneously.

The Zoom recorders are nice for live recording, but I don't know if there is an easy way to get the tracks to your phone.