Good explanation of the voicing process. But when an accordion gets tuned the tuner (repairer) should make sure that tuning and voicing are always combined. An important part of the tuning process is checking whether L, M and H reeds start simultaneously at low volume, as much as possible. I especially check playing the LH register which shown voicing issues on many accordions.I'm no expert on the subject, but it sounds like what you need is reed voicing. The reeds you are mentionig are set to sound at higher pressure - they require more air to start vibrating, which is often the case with the low bassoon reeds. When I bought my accordion, it also had this issue with some of the reeds, but I did some reed voicing and it's perfect now. When the reeds are tuned, they often get displaced, relative to the reed plate, which offsets the voicing and the reed is chocked if its tip is at the level of the reed plate, or it starts sounding later if the gap between its tip and the reed plate is too big, requiring more bellows pressure to make it sound, like in your case. Reed voicing in its essence is bending the reeds, so that you exceed their elastic limit and change their position (and the size of the mentioned gap), relative to the reed plate, but you have to be careful first not to break the reed, and second, not to place it in a position, which makes it choke. So, in summary, you should read this article, which explains it better than me and tells you how to fix it properly:
Paul, I want to ask you - on the highest tones of my bassoon switch all the reeds start sounding with the same amount of pressure, but two of them sound quieter and the last one, the A sounds louder. So, is there a possibility that, although a correct voicing is done, there still is some difference in volume and is just some inexplicable reed thing?Something else to add: when you adjust the voicing (make the gap smaller) so the reeds become more responsive (but not to the point where they choke) they lose sound volume. This is another reason why the voicing should be the same for reeds in the same "region": the ones that are more "open" sound louder but have trouble starting at low volume, and the ones that are more "closed" sound weaker but start better at low volume. An accordion is full of compromises...
Accordions are mysterious... but... the voicing is something to be checked visually. It is not very critical regarding how easily the reeds start to sound, but it is more critical for the volume they produce. But then there are also material differences between reeds, and there is the effect of the resonance chamber (inside the reed block) that can amplify one frequency more than another... It is often impossible to make all the reeds sound the same (except for their frequency). If reed block construction were approached in a more scientific way... things might improve.Paul, I want to ask you - on the highest tones of my bassoon switch all the reeds start sounding with the same amount of pressure, but two of them sound quieter and the last one, the A sounds louder. So, is there a possibility that, although a correct voicing is done, there still is some difference in volume and is just some inexplicable reed thing?
A loose and perhaps warped reed block is indeed a possible cause of weak sound, and also causes problems with the tuning of the reeds. One way to tell is to place a reed block on a glass pane to check whether the bottom is perfectly flat. Another thing to do is to put the block in the accordion without fastening at the "high" end and check whether it has any wiggle room in any direction (rotation, sideways motion). If it does then it needs "spacers" to block it in place. A spacer on top of the foot where the block is held in place (never on the bottom of course) may help prevent "roll" and a spacer at the far end of the block helps to prevent any longitudinal motion. Checking whether reed blocks are firmly in place is the first thing to do before starting work on valves, voicing and tuning. Sometimes a reed block is warped such that it does not sit firmly on the soundboard somewhere in the middle. You notice that because notes in the middle (typically around 1/3 from the lowest notes) will go up under pressure when you pull but not or less so when you push... Some accordions actually come with a clamp that adds pressure to the center of the reed block, just to ensure there is no leak there caused by warping. There is almost no end to what can be wrong in an accordion... and I'm sure you have seen all possible ways by now!I'll repeat my previous post in my comment that you have a loose or misaligned reed block. Your situation also can be caused
by a slide that does not open fully. And of course it just be time to replace your reed valves (plastic or leather).
In all these cases your situation can be corrected or repaired.
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