Concertinas can be Anglo, English, or Duet. They are fairly small, usually 6 to 7 inches across, and have buttons facing in a direction parallel to the travel direction of the bellows. Vintage instruments typically have concertina reeds, as do some modern instruments. A number of contemporary concertinas use accordion reeds with a traditional concertina action. These are usually referred to as “hybrids.”
Lachenal concertina label
Wheatstone 56-key extended treble English concertina
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Introduction to Concertinas and Accordions 