Today will be my second time recording and accordion. Last time since he wasn't playing the bass buttons I simply mic'd the treble side.  I don't yet know if today he will be playing the bass buttons. but since the sound comes out on the other side of the bellows, and they are in constant motion, what would me your suggestions for mic placement on that side?

Since I have no clue myself, I tried Google.
 
Some worthy recording and mixing tips from SOS: http://www.soundonsound.com/sos/jul10/articles/qa0710_5.htm
 
 

It spouts a lot of sound from several places.  Like most acoustic instruments, a stereo pair about 3-5 feet away is the best way to go.  Getting in close is not a great idea.  Flat condensers or ribbon mics are up to the task, nothing to sparkly or bright.   
 
I think this one was a few years back.  A single ORTF pair for the ensemble.  The only spot I used was for the guitar.  Accordion didn't need any help.
https://www.youtube.com/watch?v=sYUYb-uBcx8

They have special "bellows" microphones for accordians that are designed to pick up the sound where it matters most (near the reeds or pipes or whatever the hell are in those bloody things). The accordian player in my old band had a couple lower cost ones. Not sure what kind of mics they are or how they are inserted but they attach directly to the instrument so you have little wires sticking out both sides.
 
If you can rent or borrow some of those and then mic the room in stereo that would be cool. Otherwise probably just some higher range dynamic mics (like maybe sm57's?) or not so sensitive ribbons up close on either side pointed at the bellows then a stereo pair out in the room would probably work best.
 
The problem with condensers up close is you're gonna end up with all sorts of key and button clicks/tapping and bellows wind noise (that WHOOSH sound as the accordian gets pushed in and out). So you want definition but not THAT type of definition.
 
The room mics would be important because really the accordian is designed to throw sound and envelop the room. Like the two parts (bass buttons and melody keys) are supposed to work as one to kind of be it's own little two peice band.
 
It's a tricky instrument for sure.
 
I actually kind of want to try out one of those crazy Roland V-Accordians. They are supposedly really nice and exactly like (or better than) the real thing and because it's MIDI you don't have to worry about micing nonsense.
 
Cheers.

Thank you. Helpful info to be sure. It should be fun.

Just make them record it outside ;-)

Really experiment and do test tracks to see what works. I managed to get some "demo" quality recordings back when I was in that band but I could never really set up as many mics as I wanted (nor where I wanted) due to lack of mics and inputs (I was trying to capture the whole band so I did not have the luxury of a four mic set up).
 
Different rooms will obviously garner different results too. Accordian is one of those instruments that can sound REALLY cool if done right but it such a strange, problematic instrument to record/mic I always just wanted to play totally unplugged live to accomodate it. If I were to try it now I think I would set up as many stereo pairs as I could at varying distances and just see what worked.
 
I might even try getting a pencil condenser or two up close just in case I actually wanted to blend in a bit of that finger/button/key clacking and bellows whooshing. Could add some intamacy but I would certainly not want that overpowering the track.
 
Of course... I am no pro. Just a weirdo who played in a band with an accordian player.

I actually kind of want to try out one of those crazy Roland V-Accordians. They are supposedly really nice and exactly like (or better than) the real thing and because it's MIDI you don't have to worry about micing nonsense.

 
I recorded the same group a couple years later with one of those also.  Surprisingly good sounding instrument.  Needs a good amp for a clean sound. 
 
An acoustic nightmare in this room, but I tried by best.  
https://www.youtube.com/watch?v=doXu6aqcfFM

rumleymusic
An acoustic nightmare in this room, but I tried by best.  
https://www.youtube.com/watch?v=doXu6aqcfFM

Was the whole room like the back wall? What an echo chamber. The vocals seemed to suffer a bit, but the instruments sounded pretty good, thank you very much!
 
I enjoyed the piece. Thanks for sharing.
 
Here are a couple for you.
 
I saw this guy (Adrian Ils) and his group, Ballhaus Nuevo, at an outdoor concert in Köln (Cologne) about 12-13 years ago. Very entertaining. The first video shows the mic'ing for the accordian more clearly.
 
https://www.youtube.com/watch?v=QU643yqea6A
https://www.youtube.com/watch?v=9O0dGFKIs2M
 
and here the accordion player's playing a wired Brandoni Bottoni
 
https://www.youtube.com/watch?v=QPf4OCRb_wg
 
 

I play diatonic accordion (the Cajun and TexMex style instrument), which is a lot smaller than a piano accordion but has the same issues from a recording/sound engineering point of view.
 
Many of the clip-on or velcro-on microphones are very prone to overload. They also often have very cheap capsules indeed. The AKG ones on stems are good, but pickup pattern area might be a problem depending on the size of the instrument.
 
The best solution I've found for recording is a pair or single mic out in front a few feet away, where someone sitting and listening to the instrument might be. Using a close microphone per "end" can result in quite a lot of cross-talk and phasing issues and pick up an awful lot of mechanical noise and air swooshes. Plus a mic on the left (bass) end has the problem that the sound source keeps moving.
 
There's also the problem of balancing the two ends. The instrument's balance and tone can sound quite different to the person playing it and a person four feet away, so be prepared to have to deal with that.
 
Whatever you do, don't fall into the trap of panning the two ends of the instrument differently if you can avoid it, leave it as a mono source or very near it.