Start with the right key, not the prettiest box

An Anglo concertina gives you two different notes from each button depending on whether you push or pull the bellows, which is exactly why it sits so naturally under folk tunes and song accompaniments. Before you fall for a handsome set of ends, decide what you actually need it to do. For most English session playing, song accompaniment and morris, the choice comes down to C/G or G/D.

A C/G is the standard beginner's instrument: bright, handy for tunes in D and G, and the one most tutors and tune books assume. A G/D is lower and warmer, and many morris players prefer it because more of the melody falls on the pull. If you mainly play for dancing, a G/D is worth considering; if you want the widest choice of teaching material, start with a C/G.

Then think about buttons. A 20-button gives you the two home keys and nothing else. A 30-button adds accidentals, extra reversals and chord options, which means you will not need to trade up in a year. If the budget stretches, buy the 30-button.

Bellows: the part that decides everything

Pick up the instrument with no buttons pressed and gently draw the ends apart. A sound instrument resists slightly and holds its position; a leaky one sags open and collapses under its own weight. Now hold it up to a lamp and look along the folds. Cracks usually appear in the valleys of the folds and at the corners, so flex the bellows gently and watch for daylight. Check the gussets, the triangular leather pieces inside each fold, and the hinge tapes at the top and bottom.

Proper leather bellows are what you want. Paper or plasticised cloth bellows belong on toys. Rebuilding a set of bellows is one of the most expensive jobs in concertina repair, so a cheap instrument with tired bellows is rarely a bargain, however nice the ends look.

Buttons, action and fretwork

Press every button in turn, in both directions. Each one should return smartly and sit level with its neighbours. Feel for consistency: a worn spring feels sluggish, an over-tight one makes your fingers ache after twenty minutes. Listen for the small click of the pad closing. A sticking button is often just dirt, damp or a slightly bent lever, but check the whole row rather than assuming one fault means one repair.

Look closely at the wooden ends, especially around the button holes and the strap bars, where hairline cracks love to start. Check the hand straps for cracking and the buckle for grip, and on smaller instruments examine the thumb strap and its fixing. Anything loose here will make the instrument feel unstable long before the reeds let you down.

Reeds and tone

Steel reeds are the standard for folk playing; brass reeds are quieter and generally found in older or cheaper instruments. Play slowly through every button, push and pull, listening for weak or silent notes, buzzing, and notes that are noticeably louder or quieter than their neighbours. Buzzing often means a reed is touching its frame or a fragment of debris is lodged nearby, which is usually a quick fix.

Shine a torch through the fretwork and look at the reed tongues. Light surface discolouration is common; heavy rust or pitting is not, and it tells you the instrument has lived somewhere damp. Check the tuning if you can, but remember that many vintage instruments sit at an old pitch and will need a retune, a job for a specialist that can cost as much as the instrument itself.

New, vintage or restored?

Vintage instruments have character and tend to hold their value, but a properly restored Victorian-era box from a reputable restorer is a far better buy than an unrestored "bargain" that needs everything doing at once. New instruments from small workshops are consistent, in modern pitch, and usually come with some cover if something goes wrong. Either route works; the trap is the cheap, unrestored antique with lovely fretwork and dead bellows.

Try before you buy wherever you can. Folk festivals, local sessions and hire schemes are ideal for a weekend of playing, and a friendly player will often let you test their instrument. Take a tuner, play standing and seated, and listen for how it feels in your hands after half an hour, not half a minute.

Maintenance you can do yourself

• Keep it in a stable, dry room. Damp and central-heating heat are the two great enemies.
• Never store it tightly compressed; let the bellows rest slightly open.
• Wipe the ends with a dry cloth. Do not oil, spray or lubricate the action.
• Play it regularly. Instruments that sit idle stiffen and seize.
• Learn to remove the ends, usually six or eight screws, so you can brush dust from the levers and pads.
• Use a hard case with padding for anything more than a short trip.
• Leave tuning, reed work and bellows rebuilding to a specialist.

Buy the tightest, most responsive instrument you can afford, in the key that suits your playing, and it will serve you for decades.