The accordion reed consists of a flat plate with two slots through it, and on the end of each slot is riveted a steel or (rarely) brass strip, which vibrates in the slot as air passes over it. The strip that vibrates is called a reed, and each plate has two reeds, one for each direction of airflow, according to whether the bellows are squeezed or pulled. When you open the accordion, you will see some blocks containing the reeds. Never touch the reeds with bare fingers, as salt and acid in your skin will eventually cause the metal to oxidize. Never blow into the reeds with your breath to test them, as the same thing will happen quicker. This corrosion of the metal is one of the principle causes (among many) that will cause unwanted changes in pitch. Also, take great care not to scratch the reed plate where the slot is, or nick the slot, as the slot must have a precision fitted sharp edge to make the reed play right. Most of the reeds have a leather or thin plastic valve on the opposite side of the plate glued down on one end, to allow the air to only flow in one direction, except for the highest reeds, which, if well made, don't waste much air, and may need a little "bleeding" of air to cut the pressure. If this valve is missing or defective it will make the reed out of tune and/or sound bad.

The reeds are usually glued to the wooden blocks, called "reed bars" with a mixture of beeswax and rosin. Other kinds of wax, e.g., candle wax, pure beeswax, parafin, will not work. Some old accordions use other fastening systems, which could be converted to wax, if so desired. The unique function of the special accordion wax is to tightly grip the reed plates against the wood. This is absolutely necessary to produce strong bright sound at an accurate pitch. The wax will usually do its job well for only about 20 years or so, after which it gets brittle and starts to crack. It cannot be well restored by re-melting, as the essential oils have leached out and evaporated. If you try to fix the bad wax with a 30 watt soldering iron, it will not hold for very long, and also the accordion may sound weak. If the wax is still good, it will feel somewhat soft to the touch, and a tiny flake can be warmed and softened in the hand, and smeared between the fingers as a test. Before tuning can take place, bad brittle wax must be

A word of warning: Before buying a used accordion!! Most used accordions on the market have never been properly serviced, as this country does not have the accordion repair infrastructure of repair people, like you have for,  for instance, pianos. Pawn shops, music stores, and individuals, even some accordion dealers are selling them for too high a price. After you play an unrestored one for a while, it starts to develop bad sounds. Most accordions have hundreds of reeds and thousands of moving parts. A reed overhaul will almost always be necessary in order to tune and restore the reeds, that is, new wax has to be carefully poured around the hundreds of reed plates, the reeds inspected, cleaned, anti-rust treated, leather valves straightened or replaced, requiring many hours of work. Restoration of an old accordion can cost  hundreds of $s. Compared with piano maintenance, it is not more expensive, when one takes into consideration that pianos need to be tuned once or twice a year, whereas an accordion needs a reed overhaul after 20 years or more if properly stored and/or played nicely. If your accordion was played in smoke-filled bars every night or worse on the street corner every day, it needs to be overhauled every year or so. I would advise against paying more than $100 when buying most used accordions for the simple reason that, in the U.S. at least, very few accordions have ever been serviced, so if any malfunction whatever is noticed, don't pay too much for it. If the accordion smells damp and musty, don't even consider buying it, as dampness problems, e.g., such as arise from storage in a basement, can easily double the time necessary for restoration work . Dampness causes rust on the reeds, corrosion to mechanical parts, warping of wood parts, and on and on.

Before the reeds on most older accordions can be tuned, they must be cleaned, usually re-waxed, anti-rust treated, reed valves repaired. and reed blocks leveleled to not leak air under the block.  All of this may not be necessary only if the accordion reeds have few problems, it is relatively new and only a few reeds are out of tune. Failure to overhaul the wax and "leathers" before tuning the accordion will give a very bad result. Pouring the wax, cleaning, etc. is a substantial time commitment. The "average" or median accordion is a "3/5" 120 bass accordion meaning 3 sets of treble reeds, times 41 treble keys, 5 bass reed sets consisting of 12 bass reeds. 3 sets times 41 is 123 reed plates plus 5 times 12 (60) bass reed plates. That's 183 reed plates with a reed on each side of the plate, 366 reeds. 99 percent of American accordions have never been overhauled, and need it as the accordion wax will usually be pretty dry after 20 years. The cost of such a job, including tuning, because of the time necessary, is around $500, depending on the condition. Over time accordion maintenance is still less than piano tuning and maintenance if you consider that a piano should be tuned at least every year to prevent damage, at a cost of at least about $100 a year, accordion tuning is not expensive in the long run, compares to piano maintenance, if that makes you feel any better