A very effective modification is the narrowing of the slot (embossing). The reed slot is narrowed by pressing a round metal object along the sides of the slot, causing them to bend inward slightly.


A popular tool to use for this is the back of a tuning fork. The round ball at the end of the fork is placed on top of the reed and is moved along the reed while gently pressing down. This is delicate work and a few passes are usually required. 

Hold the plates up against the light to check the clearance between reed and slot.


If the reed gets stuck, check for rough edges either on the reed or the slot edges.
If the slot becomes too narrow it can easily be pushed back with the tip of a small screwdriver.


Narrowing the slot increases the overall responsiveness of the reed and reduces leakage when the reed is choked. The reduced leakage has a very big impact on overblow playing.

before embossing (click to enlarge)
after embossing (click to enlarge)

User Contributed Notes
20-03-2016 22:11
Tinus: I embossed hole 4 on my 'A' harp and i embossed a bit too much. So i did what i did on my 'C' harp and got a screwdriver in to push the slot back in a bit. However no matter what i did i couldn't eliminate the catching as the reed went through the slot. I think maybe there were some burrs left so i scraped around the tip area of the slot and that eliminated the catching. However after setting the gap of the reed and retuning it the sound sounds a bit more muffled and not as loud as the other blow holes. It may be there is still a bit of friction somewhere but it's hard to see. Anyway tomorrow i'll take it apart again to see if i can improve the sound. Sounds more dead than it did before, that's the best way to describe it.

As far as burrs do you get that happening after you emboss? I saw someone else emboss and they said it's best to use like mineral oil to help avoid it. Have you heard of that? Also how do you decide when you've embossed enough? Do you do it until you only get a sliver of light around the reed or is there some measure you aim for? Sorry for all the questions!

17-03-2016 02:22
Tinus: I'll have to check out how straight the reed is. I think it's pretty straight but i'll check it again. Does the tip need to be a hair higher though than the rest of the reed? Or can it be dead straight? I have the 4,5 and 6 reeds dialled in pretty nicely and they rarely stick at all as i found a nice balance. The #1 reed though has always been a problem, mainly always to do with it sticking and not releasing for the normal blow note.
I haven't really pursued tip scooping much so far because i really don't have a tiny file that's suitable. I have very small needle file type things but i think they're still a bit too large for doing it. The one i saw you doing it with in the video looked really ultra thin. Oh i meant to say; on your advice i bought one of those tuning forks with the ball on the end. Makes it so much easier to control the embossing. That was a cool tip.

17-03-2016 01:06
@Gary: it helps if the reed is very straight. Also a little tipscooping helps to stop the condensation forming a film between the reed and plate.
16-03-2016 17:20
Thanks Tinus. I did the hole 1 blow and draw slot today to help with the OB and it definitely helps but i'm still having the problem of being able to get the OB and still have the blow reed return for normal playing once i release the choke. A lot of the times it sticks with the condensation and i have to play the draw reed hard and bend it which resets the blow reed back but obviously i can't play like that with the normal note sticking a lot. The only way i can stop that is by raising the action of the blow reed but then of course it's very hard to get the OB. It's a fine balancing act and a compromise is hard to find. it's a handy note to have for the flat 3rd in first position in the bottom end of the harp.
16-03-2016 11:05
@Gary: I always do both plates but doing just the reeds you want to choke will also work. I just like to get everything as uniform as possible.
16-03-2016 03:07
Tinus about embossing; is it best to always do the draw reed slot as well as the blow? If i only did the blow slot would i not get any benefit from the procedure?
09-03-2016 19:49
Cheers Tinus. That's a great tip, i wouldn't have thought of using the feeler guages for that. I was listening to a lot of the tracks you recorded on YT last night. Wonderful playing and tone. Thank you.
09-03-2016 18:04
@Gary: I use a feeler gauge. a thin one. put it between the reed and the slot to turn the reed. Much easier to get right than a spanner. I used to turn the reed with a small screwdriver and a hammer; place the screwdriver agains a corner of the reed's rivet pad and gently tap with the hammer.
09-03-2016 17:52
Thanks Tinus. Can i ask what you use for centering reeds? I've seen guys use a tiny little thin spanner but i have never seen those on the market where i live. The only one's i've seen for sale are on the web site of a guy from the US! It's a bit of a hassle sending over there for a tiny little thing like that. I thought about using these small pliers that i used to work on mountain bike forks for removing circlips. They have very small thin tips, that might work, but i haven't tried them yet. I'll have to see if i can find them first as i haven't used them in years.
09-03-2016 13:50
@Gary: I hold the plates up to the light to see where the reed touches. sometimes it helps if you push the reed down a little so it comes closer to the plate when you inspect it.
08-03-2016 20:48
Cheers Tinus for the reply. I have it going good now the OB is really pretty easy to get, on a C harp i'm doing this. The only problem i have is with getting things tight in the slot i'm getting a tiny little bit of that sound when the reed is just slightly hitting off a burr or one side of the slot. It makes a tiny little clicking noise which is not really audible on full power but you notice it more breathing softly into the harp. Trouble is it's soooo hard to nail down exactly where it's happening as it's so hard to see!! I look through a magnifying glass and i also have a jewelers loupe. Even so it's still hard to nail down the exact bit that's causing the problem. It's pretty minor, but when you want everything perfect, annoying nevertheless. How do you see really close do you use special magnifying tools to see up close?

07-03-2016 03:42
@Gary: hey Gary, I thind the deformation of the reed is the most important thing. The top edge is what deforms and it does help but I think the dip of the reed at the rivet end is more important.
07-03-2016 03:32
Hi Tinus. I embossed hole #4 on my harp tonight to try to get the ob to pop out easier. So i used a round handled spoon and ran it up and down the slot a few times, not that many actually. So on checking i noticed when pressing the reed in i was getting that slight catching as if the reed was either hitting the edge or a burr. I tried pushing the edge back in with a small screwdriver but it didn't move it at all. I used a small needle file to gently file and that cleared it up pretty much. Anyway i noticed the OB is easier to get now but i don't know if it's because of the embossing or the angle the rivet end of the reed is now taking going down into the hole as a result of the embossing tool pressing the reed down there. As far as OB's what do you think makes the most difference? Embossing or one of the other techniques? When you emboss what part of the slot is actually bending in? Is it the top of the slot? Or is the pressure forcing the middle of the slot further in towards the reed or is the whole side of the slot moving in and narrowing? I'm asking that because as i said above when i go too far and the reed kind of binds i try to press the inner part of the slot out again but i don't seem to get any noticeable result from doing that.

Sorry for all the questions but getting my harps set up for overblows and overdraws is kinda an obsession with me!

Cheers Tinus.

14-10-2015 22:18
@uri: the session steel plates are not steel but german silver, wich is a type of brass. It can be embossed but it needs a little more force.
14-10-2015 20:25
hi tinus,
I tried to emboss a session steel reed plates, but the effect is neglect. I believe it is because of the steel being much harder to reshape than brass. how do you work with this kind of reed plates?
24-09-2015 19:56
@Gary: Yes I have heard of people using all kinds of things: marbles, ball bearings, wrenches, spoons tuning forks. Basically anything that is hard and which you can press down on the reedplate will work.
23-09-2015 04:29
Tinus i saw a guy on YT using a marble to emboss the reeds. Have you ever heard of anyone using that?
13-09-2015 09:34
Yes, best to start on old plates to get a feeling for how much pressure to use.
13-09-2015 04:36
Thanks Tinus. The embossing is difficult. Definitely a lot harder than it looks. It's easy to mess up a reed plate doing it if you're not careful.
12-09-2015 20:27
@Gary: I use the other side of the fork to get into the corners of the slot. I usually use a watchmakers screwdriver to push back the sides of the slot if I have embossed too much. The other tool I use is a feeler gauge. I think they are used to adjust sparkplug timing or some such thing, but most hardware stores have them and they are not very expensive.
12-09-2015 03:58
Tinus what are you using the other side of the fork for in the slots? You emboss with the ball end but then you also used the other side for something. Also what else can you use to emboss? I used the round ball end of an allen key, but it's not very good. I'll have to find something else. I have a bit of work to do to get my harp back into shape after doing this! I think i leaned on it too heavily and reduced the gap way too much. No sound at all from a lot of the reeds, blocked in the slots. I had to use a really small file to widen the slots enough to get the notes to play without being choked off. What is the other tool you're using there? It's like a small screwdriver or something and what are you doing with it?
05-12-2013 16:07
Yes I will make a list. Will post it soon.
02-12-2013 05:58
tinus, would you send us a list of the tools needed to do this stuff like the feeler gauge and what you use for tuning afterwards? what kind of tuner do you use?
27-11-2013 17:55
Noel "digger"O'Dell
I have been playing and blowing on the harmonica for seventy one years .I am glad to see the word choking on over blow .com . now days it is called cross harp. Deford Bailey used it many years ago on the Grand old Opry. I have learned a lot from you keep up the good work. Digger
01-09-2012 11:39
@Jon: I don't use the feeler to get the gap, just to support the reed and sometimes to adjust it. The right gap is found by trying how far the isolated reed bends and how fast the reed responds when going from normal play to overblow and back.
31-08-2012 15:18
Jon Erickson
In one of your videos, I saw a feeler gauge. Is there a gap (e.g. .001, .002) you shoot for when embossing?
16-07-2012 00:08
ok, thanks a lot
15-07-2012 22:12
15-07-2012 13:03
thanks, but a few more question
which sequence should the harp modification be?
is embossing to arcing to gapping right?
can the tip scooping and corner rounding be ignored?
14-07-2012 03:03
the side of the plate where the reeds are. Gentle means that you press down but not to hard. Press to hard and the reed will get stuck.
14-07-2012 02:32
which reedside?
and by gently does that mean dont exert pressure while embossing?
09-07-2012 12:56
Both reeds on the reedside of the plate.
08-07-2012 13:53
excuse me, is it that both the draw reeds and blow reeds are to be embossed above the rivet? or is it under the rivet?
20-03-2012 13:09
No I don't, too much trouble not enough effect.
20-03-2012 03:33
yo lo hago del otro lado del reed plate tambien. usted?

I do the other side of the reed plate too. you?
23-01-2011 14:43
Mr Jones
Just wanted to say you're awesome!
20-10-2010 23:56
@Kieron: 1.yes it will affect the overblow.
2. yes you can, try making an indentation along the top of the slot about 5 micron from the edge of the slot. That should push the edge inward.
If the reed gets stuck make sure it is aligned properly, check for tuning burs and if after that it is still stuck gently push back the slot edge with a small screwdriver.
18-10-2010 20:22
Hey Tinus, If there is too much of a gap between the reed and end of the slot:

1. Will this effect overblows?
2. Can you emboss the slot end, to close the gap and what should you do if the reed gets stuck through over embossing?

Thanks in advance.

04-08-2010 23:25
No there is no avoiding it but since I always do this before I tune the harmonicas I don't think it is a problem. The effect of this is not so big that it exceeds the normal tuning tolerance that a factory tuned harmonica has.
04-08-2010 22:23
Hey Tinus,

When embossing, how do you avoid scraping the reed itself when you are running the rounded tool back and forth along the slot. It seems impossible to emboss more than 20% of a slot without scraping the middle of a reed in doing it... I see in the picture above, it seems your reeds have a scrape down the middle as well. Is there a way to avoid this/is it necessary to?

23-07-2010 12:29
Embossing,Tip Scooping,Corner Rounding, Waxing, Arcing and Gapping
23-07-2010 10:53
I was reading the comments and the last one said the order of which the customizing process should be done. But I also saw a process named Tip Scooping. Where would this process fit in the order?
01-05-2010 17:54
Embossing, Corner Rounding, Waxing, Arcing and Gapping
01-05-2010 04:49
Thank you for the site - very good and precise information!!!

What is the right order to implement these steps?
Corner Rounding, Embossing, Waxing, Arcing and Gapping - What order do you usually do?
12-10-2009 13:57
Embossing improves the responsiveness of the reeds. That is useful for all notes.
12-10-2009 13:46
Does embossing only help when using the overblow technique or will it improve the "regular" notes as well?
30-09-2009 22:52
I emboss all the reeds
30-09-2009 22:37
Justin McMillan
Hey, this may be a stupid question, but are you embossing the draw reeds or the blow reeds?
17-09-2009 11:09
Hi Tinus, congratulations great site...I have a harp with some notes out of tune. How can I sharpen or flaten a reed on my harp t tune it ? Thanks.
01-09-2009 21:23
will embossing make the higher notes on my harp easier to play?
05-07-2009 00:48
You either embossed too much so that the reeds are now stuck or the embossing caused the reeds to bend down into the reedplate and you failed to gap and arc them after embossing.
04-07-2009 22:37
I tried to emboss my Hohnerbleusharp t find out i couldnt breath air trough the plates, did I do something wrong?
21-06-2009 18:54
Scrape a fine screwdriver allong the reedplate slot to widen the slot again. Check against the light to see where the problem is.
21-06-2009 18:49
I embossed the 3 draw slot and now it keeps ringing and sounding completely shitty. i tried readjusting the reed so its completely in the middle of the slot but still its kaputt. i need this harmonica to play properly for my concert.
07-08-2007 13:03
es estupendo enhorabuena y gracias por tu pagina
29-08-2005 01:56
richard l. vale
Tinus: Your instructions are excellent. A great website!
28-08-2005 15:32
I forgot to add my address in the threadfollower; it's sorted now :-)
28-08-2005 14:52
If you look closely you can see that the embossed slot is a little wider near the rivet end. There is also a glob of wax on the rivet end that obscures the view a bit. When emossing I don't pay too much attention to deforming the reed, if I bend the reed into the slot when I emboss I don't care because that is needed for my way of arcing the reed anyway and that is probably why I can get closer to the rivet end.
28-08-2005 12:21
Seeing these pictures, I realize I can emboss much more drastically than I did so far. Also, I wonder how do you get so close to the rivet end?
26-08-2005 16:58
The pictures have been made. I just have to scan them and upload them. The next few days you will probably see a flod of new images on this site
03-03-2005 01:43
Good suggestion David, I am working on it. I do understand that a picture says more than a thousand words, the only difficulty is taking the right picture :-)
02-03-2005 10:45
David Bullet
I need information about modifications in harmonica whit pictures please.ok....best of luck the graet site David Bullet from Brazil/Rio de Janeiro