English concertinas play the same note in each direction. That is, each button plays the same tone whether you’re moving the bellows in or out. Each end has a thumbstrap and a pinky rest for supporting the concertina, leaving your other fingers free to play.
English Concertina: Keyboard Layout
On each end of the concertina, the two middle rows are equivalent to the white keys of a piano; the two outer rows are equivalent to the black keys.
If you can visualize music written in standard notation, all of the notes on the lines of the musical staff are on the left; all of the notes on the spaces are on the right.
To play the C scale, you would find middle C and walk your fingers up the middle rows, alternating between the left and right sides. Playing the G scale, which has an f#–a black note–you would start on g and do the same thing but reach out to the outer row for the f#. It’s a logical layout, and many people find that the buttons fall naturally under their fingers.
A 48-key treble English concertina has the same range as a fiddle/violin and is fully chromatic. Treble concertinas with fewer buttons generally omit the top octave, more or less, and some will omit one of each of the enharmonic pairs. So, for instance, you will have an g# button, right there next to the g, but you won’t have the corresponding a-flat button on the other side of the concertina. You will have the sound, since a-flat sounds just like g#, but instead of being next to the a, it’s on the other side next to the g.
English Concertina: Variants and Strengths
You might also encounter tenor English concertinas, tenor/trebles, extended trebles, baritones, and, rarely, maybe even a bass concertina.
English concertinas are great for playing single-note melodies. You can play chords, too–just press down two or more buttons simultaneously–but it takes diligent practice to play melody and chords simultaneously, since both hands are playing melody. Because English concertinas are unisonoric (play the same note push and pull), they lend themselves to playing smoothly, and because they’re typically chromatic, they’re useful for playing music with lots of accidentals.

Lachenal 48-key treble English concertina