Somebody landed on this blog today after searching the question, how to add more tremelo to diatonic accordion reeds. Good question. I happen to have the answer. The amount of tremelo has everything to do with the tuning.  Accordions have 2 or 3 or even 4 reeds for each key or button, tuned octaves apart. For very little tremelo – dry tuning, you want the pitch to be exactly or very close to exactly octaves apart. If you tune any of the notes a tiny bit sharp or flat, you get tremelo. You can find a much better explanation than I can give on Hans Palm’s Accordion Page.

In my experience, many Portuguese players like to have the wettest tuning, that is to say the most tremelo. I’ve heard that sound referred to as “wide-open musette”. It’s become a characteristic of their folk music. Here’s an example I found on YouTube.

If you tried to tune your accordion for any more tremelo than this, it would sound out of tune. Here’s an example of much drier tuning.

It’s much crisper and cleaner without much tremelo effect.

So the answer to the searcher’s question is to take the accordion in to a good tuner who will make the adjustments by scratching or filing the reeds. This is time consuming and can get expensive. It’s best if you know the kind of sound you’re after when you buy your accordion and you get one already tuned the way you like it.