I'm guessing it's a bayan, but I don't play accordion. I don't get what you mean about holes, though, they all look like extra buttons, and it seems like he's just playing one per note.

look like buttons*

I'm pretty sure standard button accordions are diatonic on both ends instead of just on the bass end like a keyboard accordion, but I've never played one.

Oh, buttons then. I thought they were holes. Shows how much I know from accordians :P.

Yeah, they're buttons, and what part are you referring to, where he's playing the same note over and over again? The palm-muted section of the chorus riff? I think he's playing that note with two fingers, to better simulate alternate picking; those notes are fairly quick, and I'd imagine it'd be quite difficult to chug away like that with only one finger.

I've never played an accordion that size, but my grandparents have a small button accordion, and as OZ suspects, the melody buttons are indeed arranged diatonically (that is, each button corresponds to a note in a single given major scale, and incidentals are left out) They're confusing as fuck and I still can't figure out how the damn things work, so don't feel bad; I doubt even Google would be much help.

The chord/bass buttons on a keyboard accordion are arranged in the circle of fifths, so the buttons immediately adjacent to C are G and F, which makes most simple chord progressions easy to play. I've never played a right-hand- button accordion, but apparently there are a couple of different systems, none of which seem to make any logical sense upon initial investigation.

I play accordion, and have one like this (Bayan). It's a good system but a weird one. The left hand, the 120 buttons, are like the guy above said, organized in the circle of 5ths with C in the middle. C down goes C, F, Bb, Eb, Ab, etc, and up goes C, G, D, A, E with the 4 rows out from each individual note making a chord, major, minor, 7th and diminished. (there's a second row of individual bass notes called counterbass, making the whole thing a hair more versatile). Bayans also often have a converter system making the left hand into entirely individual notes, arranged much like the right hand, diagonally.

The right hand where a keyboard usually is, has about 70 notes (piano accordions have typically 41, up to 47), and they're arranged down in minor thirds (C, Eb, Gb) and at a diagonal chromatically (C, Db, D, Eb, E, etc.). The benefit to this button system is that you basically have a whole octave or more within a 4 inch span, instead of stretching your hand all huge like on a piano.

The buttons/keys lift open a leather covered thing over a hole, the hole being for air to pass through the reeds like in a clarinet, harmonica, etc.

This button accordion is not "diatonic", diatonic is like the common Mexican style, those play 1 note going out with the bellows, and a different note going in with the bellows. This accordion does the same note in/out.

Thanks for the explanation, catpenis. I was wondering what the advantages would be of having buttons on the right hand. I didn't play accordion long enough to get that far.