Inside an Accordion Bass Mechanism

I needed a part so I started to dismantle an accordion bass mechanism that I had in my accordion graveyard. Most piano accordions have Stradella basses comprising 2 rows of bass notes and 4 rows of chords.

Accordion Bass Mechanisms

Each button in an accordion bass mechanism has a flat shaft with pins that operate levers to sound the appropriate reeds. In the picture above the shaft on the left has 4 pins so I suppose it’s from the 7th chord row and the ones with 3 pins are from the diminished chord row. Looking at the picture the shafts are out of order (4 pins and 3 pins should alternate) so it’s a good thing I never intended to rebuild it! Most accordions use a 3 note 7th chord but this Marinucci must be like a Weltmeister and have a full 7th chord. (I never heard this accordion play because it was given me for spares and it immediately had all it’s reeds taken out!) I do accordion repairs for private customers and The Accordion Shop. If you want help mending an accordion yourself try this great website run by George Bachich.

Why Remove an Accordion Bass Mechanism?

You might have to remove the bass mechanism on an accordion because it’s the only way to work on the pallets below if they are broken or leaking.

After removing the 7th and Dim buttons I found that I could get the Major and Minor chord buttons out in one go. I was just breaking this old Marinucci for parts so I knew I would never have to re-assemble the bass mechanism. If you did need to re-assemble, you would have to carefully keep track of each part.

Removable Accordion Bass Mechanisms

This modern Hohner has a removable bass mechanism – you can get this far very quickly by undoing 6 bolts! The pallets are under a protective aluminium plate. Most Scandalli and Weltmeister accordions also have removable bass mechanisms

This Scandalli Scott Wood Four is old (40’s I think) and amazingly they had already developed a removable Stradella bass mechanism.

The Deeper You Go…

The last 2 rows of buttons are the bass buttons and have the longest shafts. I found them hard to remove without bending some of them. In this case bending parts didn’t matter but it might be tricky if you are intending to re-build.

I needed to dismantle this Vignoni bass mechanism and it took so long that I had to leave it overnight. I had nightmares about a cat walking along my windowsill and muddling the bass shafts. (We don’t have a cat!) Come the morning I managed to re-build it without too much trouble.

Rollers or Pipes

Last of all I removed all the “rollers” or “pipes” These are the 24 long bars (in the centre of the picture below) that lift each of the 24 pallets and have levers where needed to be activated by a button. For example the C pipe associated with the chords would have levers for all buttons playing a chord with the note C in it – like C major, C minor, A minor, Ab major etc.

To be honest I’m unlikely to need any of the complicated bits for repairs because they tend to be slightly different on every accordion, but I have a store where I keep bits and they sometimes turn out to be useful. For now I’m just glad I don’t have to rebuild this accordion’s bass mechanism!