Gapping and arcing is not something you can do well by just looking at the reed. You have to feel how the reed responds. Gap and play the isolated reed, bend it down and choke it. Listen for the escaping air or feel the air flow by holding a finger a little above the slot.

I use two parameters to check if a reed is set up the way I like it.
The first is the distance I can bend the reed before it chokes, the second is the amount of air that escapes along the reed while it is choked.

I try to get the isolated reed to bend at least a quartertone, maybe a little more, before it chokes.
When it chokes there should be as little air leakage as possible. The reed will never fully close the slot, but there is a big difference between a howling wind and a soft breeze.

I like my reeds very straight and the gaps very low, so arcing usually means getting rid of the arc the manufacturer has put on the reed.

I have found that I get the best result when the reed is dipped slightly at the point where it leaves the plate, near the rivet, and comes up straight after that.

Sideview of a new reedplate (click to enlarge).
Sideview of a plate after arcing.

Narrowing the slots will very likely have bent your reeds out of shape. The reed will probably be bent down into the slot, curved around the edge of the plate.
When bending it back up, make sure the reed doesn't bend back at the rivet but just a little past the edge of the plate so that the curve around the edge, causing the reed to dip into the plate, remains in the reed.
The curve at the edge of the plate is very small and hardly visible, but the effect on the leakage of the whole reed can be dramatic.

After this point I try to get the reed to be as straight as possible, always aiming to get as little leakage as possible from the reed when it is choked.


All this is a matter of trial and error, so I suggest you get a pair of old plates to practice on before you tackle your favorite harmonica.

New plate.
Plate after embossing and arcing .
New Plate.
Plate after embossing and arcing.
User Contributed Notes
21-07-2016 17:10
Thanks Tinus. Yeah i really notice it after playing the C and D harps for a while. Going back to the A and practicing triad arpeggio's in cross position, which i'd been doing no problems on the higher keys, was so much hard work. I will say though i find the #9 overdraw to be easier on the A harp. It seems to pop out with great volume and not much effort.
21-07-2016 14:45
@Gary: yes most people find the lower harps more difficult to overblow, but usually that is especially hole 1. The low harps have the same reed length as higher harps so the reeds have to be more flexible or weighed down at the tip to create the lower pitch. This usually means that the reeds are more difficult to choke.
21-07-2016 05:33
Tinus i have my D and C harps set up to OB well. However i notice my A harp is much harder even though i've embossed it and gapped it. The hole 5 is particularly hard to grab quickly. If i gap it tight to get the OB then the normal blow note is sluggish to respond or sticks. Have you heard of the lower key harps being tougher to OB on?
18-02-2014 15:28
@Austin: I would start by closing the gapps completely so that both blow and drawreeds don't play at all. At that point you should have very little leakage. From there I would slowly open up the blowreeds until they play well. after that work on the drawreeds until they can bend down about a quarter note.
The arc of the reeds is very important too, try to get the reeds as straight as possible.
18-02-2014 07:46
I tried arcing my reeds and it worked well on some, but I'm having leakage and response time problems on my 9 and 10 draws and blows and my 7 blow is leaky and bends too easily. What would you recommend I do to fix it?
- Austin
23-12-2013 01:58
@Francesco: arcing is probably what you need. The reeds are stronger then you think, but caution is good.before you start just see how well the reed chokes when you isolate it. That is the important thing; check how much air escapes when the reed is choked.
22-12-2013 16:22
Hi Tinus and thanks for this very useful site! Though I find quite easy to overblow only by gapping (no arcing) I find my overdraws (hole 7 and 9) very tough and uncertain. I tried some arcing but the reeds are very short up there and I'm afraid to break them. Do you have any suggestions?
11-09-2012 17:57
The arc is made so that minimal airloss and maximum responsiveness are balanced out. There is an optimum. Less arc means less airloss but can also lead the less responsiveness. Try to find the middle ground.
11-09-2012 09:39
one more question which confuses me most about arcing, u stated arcing means getting rid of the arc, someone i asked said to put an arc. maybe i still cant get a clear picture of how an arcing should be despite pics provided, do u have any idea?
29-08-2012 15:59
both, the blow reed to choke the draw reed to play.
29-08-2012 15:38
I have a question,if I arc for overblowing, should I arc just the blow reed, or both blow and draw reeds?
24-06-2012 23:35
@Duane: gapping and arcing combined is the key. Straighten out the reed and then gap it tightly that will change how far the blowreed bends. The gapping is the most important part.
24-06-2012 07:50
Thank you for all your help on this site!!

Quick question: Is arcing the main or only technique to set the point where the blow reed chokes? I keep fiddling with arcing one reed (Blow #4) and it seems to consistently bend at least a whole step before choking. . . Embossing further won't change that, will it?

I try to not to ask anything that hasn't been covered elsewhere here, but I looked all around and I think I'm the first for this question. :-)

Thanks again!
27-03-2012 01:55
@Don: better use some bluetac next time.
26-03-2012 15:30
DO NOT USE wax if you plan on playing outdoor gigs in hot weather or if you leave your gig bag in the car during the summer. The wax melts easily and will screw up all your harps. I found out the hard way when I was on stage in front of hundreds of bikers and NONE OF MY HARPS WORKED! Every single harmonica that I used wax to seal rivots on where completely dead. I spent hours and hours cleaning them out. Once that wax gets down into the slot and onto reed it's a real bit$h to get it out. So again, if you play outdoors in the summer, better keep your harps cool, or you'll be swearing in multiple languages like I did!
14-07-2010 20:42
thanks a lot this improved my bends too
19-05-2010 03:22
Thanks tinus,
but believe me if u try to drawbend holes 2 & 3 by lawering your lawer jaw
your throat will open much wider and your back tongue will go down making a bigger chamber and you'll be able to bend stone reeds.
but as long as you told me not to do it, i will abide by your rules master :)
18-05-2010 01:43
In order to adjust the point of transition you isolate the reed. That we you can find out precisely how far it bends. You set the drawreed up to bend well past the half step and the blowreed to bend almost to the half step.
Don' move your jaw when you bend, try to do all your bending from the back of the tongue/top of the throat.
Maybe work on your technique more then on the harp :)
18-05-2010 01:37
wow, that was helpful like a CV for the reeds.
but tinus i didn't get the part of the transition.
how can i feel it to modify?
so if the blow reed is participating quicly,
will it be faster and esier for the draw reed to respond for bending down on hole 2 and 3 ?
anyway on holes 2, 3 i open much wider my lawer jaw when draw bending down after the 1/2 step down, don't know if i should set the reed for my technic or not cz it sucks the bending air powerfuly tightly.
regards, thanks
08-05-2010 15:07
If the tip of the reed is curved up the reed will be easier to get to sound. The straighter the reed is the harder it is to play and the easier it is to choke. However if you play the reed as part of a bend or an overblow (in opening mode) it will be easier to control if it is straighter and it will have a clearer tone.
The reeds work together, the tighter the blowreed is gapped the longer it will participate in the bent note. You can adjust where the transition between the blow and draw reed happens by opening or closing the drawreed. I suggest you try a few. I try to make sure that the transition never happens on a note. So not on the halfstep bends but somewhere between the half and hole step bends in hole 2 and 3.
07-05-2010 05:36
hey tinus i use this site (lickbyneck.com) to learn some bass lines to play with standard jazz songs. Give it a try you will like it
07-05-2010 05:32
hi tinus, i saw you in the arcing youtube video arcing the 1 & 2 draw reeds(the middle of the reed goes far from the plate).
ruppet oysler recommands curving not arcing(the middle of the reed goes towards the slot).and it is obvious that curving closes the slot for tightning the air.
i am realy lost, what result gives each one?
what should be done to the draw reed to have an easy drawbend response after gapping close the blow reed specially on hole 2 and 3
thanks forward
02-10-2009 23:54
You resonate on all the notes and I don't warble so I can't help you with that.
02-10-2009 23:37
Billy V
WOw I did not know that. How do you resonat on the draw? AND How do you warble. Can you resonate back and forth that fats?
02-10-2009 23:21
No you don't loose notes. There is another reed that takes part in the bent note and that reed doesn't choke.
02-10-2009 23:16
Billy V
Ohhhhhhhhhhhhhhhhhhhhhhh WOw. I see. You have to play the blow notes by resonating if you just blow they are suppose to choke. Got it. ANother Question. You said you like to have the gap on them and arc so it bends a quarter tone before it chokes. Even for the three hole. But do not you loose notes?? THANK YOU so much it helped so much
28-09-2009 00:15
I think you are reading the pictures wrong. In the before picture the reed is sticking up (bent up) in the after picture the reed is almost flush with the plate. The reed isn't perfectly straight because if it were it wouldn't play at all. And yes with the reeds closed they are more likely to choke, this is the object. They have to choke otherwise they won't overblow. Playing them normally requires you to learn to resonate the normal note carefully before playing the note. That way it won't choke. This is easier to do when playing softly and needs some training when playing with volume.
27-09-2009 23:27
Billy V.
If you say you like to straighten them why do you have pictures before arced (straight) then after arced (bent). Am i missing some thing. Really we should go in the reverse order of your picture right? We want them straight no.(for good over blows and ovwer draws).

Also in setting up your harp to do these will undoubtely play sticky in some notes.In my other comment I explained one of my problems.
07-08-2009 12:15
See the next page for a description of the wax that is attatched to the rivet:
07-08-2009 06:33
In my opinion, in oder to easy overbands, we put something on blow reeds.
but you painted on the draw reeds.
why are you doing?
07-08-2009 06:22
Thank you.
Is it just practice Item, the wax?
Are you using the wax harmonica when you perfomance?
I can't believe your clear overband sound!!
01-08-2009 11:51
01-08-2009 11:43
Yes buy wax
01-08-2009 06:18
Sorry, I can't English well. If i want to overbands, should I buy the wax you sell? or any wax?
please more simple answer. korean diatonic harmornica technical is very low. but my teacher and I learned overbands, but we need more smooth sound like you. thank you
31-07-2009 12:31
See the next page for a description of the wax that is attatched to the rivet:
31-07-2009 06:41
Thank you for your kindly answer but i dont understand well yet.
is it paraffin?or bonding?
what's that something on the reeds?
31-07-2009 02:39
Above below? I don't quite understand your question but I can say this:
If you mean the blow and draw reeds then yes.. you adjust both the reeds. If you are saying does it arc up and down then yes. The arc is very slightly down at the rivet then up at 1/3 of the reedlength from the rivet and then straight out for the rest of the reed length.
31-07-2009 02:31
31-07-2009 02:30
Should we put the arcing on both obove and bottom?
31-03-2009 19:53
André Costa
Why cant i see anymore the pictures?or ti's just a problem of my computer?Do you have any advices for me to solve this problem?
19-12-2008 00:55
The gap is different for each and every reed. It depends very much on how far you want the reed to bend. The closer the gap the shorter the bend of the normal note is the basic rule. However in many cases the two reeds in the slot work together. So for example the draw 3: you need to be able to bend the draw note quite a bit so it has to be open a bit but the bend is produced by both the draw and the blow reed so the gapping of the blow reed is also essential. In the 3 draw it is indeed so that the blowreed is gapped closer. This is not true for every reed pair because in the higher reeds (above hole 6 on a richter harp) the opposite is true. Alot of it is indeed trial and error, but the important thing to realise is that both reeds work together and any change to one has a direct effect on playing the other.
18-12-2008 21:40
Hi Tinus

I am just getting into harp modification and wondered which plate sto gap, arc, and set up first. The blow or the draw reeds? The blow reeds are supposed to have a larger gap right? Is it a case of try the blow then the draw until you get both responding properly.

Many thanks

Great site!
03-08-2008 15:39
Wow, thanks for the quick reply. Thanks
03-08-2008 15:20
I bite my nails since I am a constant worrier, so no I use a small watchmakers screwdriver that has the same width as the reed. So I use a finger on top of the reedplate and the srewdriver below the reedplate.
03-08-2008 15:11
Hey Tinus. Would you just use you fingernails to gap and arc?
26-01-2007 20:52
Thanks very much Tinus! You are helping me very much.
If someday you come to play here in Brazil, please let me know.
26-01-2007 16:58
A stuck reed can have a lot of causes. The reed could be badly alligned, if the reed is not in the center of the slot it can hit the edge of the slot and get stuck. Tuning the reed can cause the reed to have small blemishes allong its edge, sometimes this is enough to get the reed stuck in the slot. Ofcourse other things like pieces of chicken can get stuck between the reed and cause it to stick.

However the main reason for a reed to be functioning badly after gapping or arcing would be that it has been gapped too tight. The reed needs a tiny offset from the plate in order for it to be accelerated enough to allow it to pass through the plate. If the gap is too tight it becomes very difficult to play the reed.

Problems of the first kind kan be detected by simply holding the reedplate against the light and checking for contact between the reed and the reedplate or for foreign objects.
If it is the gap that is the problem just slightly widen the gap and your problem should be over.
26-01-2007 05:01
The 7th draw reed is not sounding loud as the others...It seems it is a little stucked. Can you help me? Thanks!
26-01-2007 04:38
Hi Tinus!
I am new to harp modifications.
I was trying to arc my A harmonica but the 7th draw reed stopped bending down...How can I fix it?
Your site is very good.Thanks!
14-12-2006 00:44
> Peer
Es tut mir leid aber mein deutsch ist wirklich nich gut genug um die info im Deutsch zu ubersetzen. Ich hoffe das du mit der hilfe fon babelfish oder ein anderen translator die info doch verstehen kanst. Wann das nicht hilfst kanst du mir naturlich ein email schicken und dan versuche ich im meinem steinkohlen deutsch ein und anderes zu erklaren.
12-12-2006 22:17
Peer Engström
Lieber Tinus,
mit großer Neugier und Interesse habe ich versucht deine interessanten Informationen
über das modifizieren der Harps gelesen.Ich habe leider nicht alles richtig verstanden wegen dem englisch.(Fachbegriffe) Wäre überaus dankbr dafür,wenn es eine Möglichkeit gäbe,die Ifos in deutsch zu erhalten.Vielleicht hast du eine Idee das zu machen.Ich finde deine Site großartiig.
Herzliche Grüße Peer.
04-04-2006 01:43
When I arc a reed I mostly use my fingers and a small screwdriver, preferably one that is more or less as wide as the slot because that way I have less change of causing an uneven arc.

If the tip of the reed is turned up I hold down the tip and the rivetend with a finger and push with the screwdriver from under the plate in the middle of the reed.

If the tip is turned down too much I just pus with the screwdriver at the tip (from under the plate) while holding the reed down at the rivet.

All this is rather subtle work ant takes some Fingerspitzengefühl.