The Orla expander offers the following: 
This expander is especially suitable for the accordion.  It looks complicated but is intuitively laid out section by section and is easy to use.  The expander allows layering of sounds (many at once) even when the accordion only has 3 channels (treble, chords and bass).  Recommended by us to give a full sound straight away from your accordion.

6 Sound sections, 
Right 1 - first sound for treble keyboard.
Chorus on off, sustain on off, Octave change.
Electric piano, steel guitar, rock guitar, synth brass, horns, sax 2, clarinet, piano, jazz guitar, nylon guitar, brass, trombone, sax 1, vibes, marimba, slow strings, jazz organ, rock organ, American tremolo, bandoneon, organ, accordion, strings, scat, cathedral, cassotto, tremolo, celeste, French, master 
User setting provides provides another 30 sounds.
Volume setting for Right 1
Right 2
Portamento on and off, Polyphonic / monophonic on and off, Octave change.
Pan flute, clarinet, oboe, sax2, sax3, sax1, trombone, trumpet, flute, synth1, synth2, harmonica, rock guitar, Hawaiian, violin, jazz guitar, bassoon, mussette, synth 2.
User setting provides provides another 18 sounds.
Volume setting for Right 
Flute drawbars
16 foot, 5 and a third feet, 8 foot, 4 foot,  an 2 thirds, feet, 2 feet, 1 and 3 fifths feet, 1 and a third feet, one foot - drawars for each of these footages.
Flute bars on / off, Organ 1 on / off, Organ 2 on / off, Organ 3, Organ 4 on / off,4 feet on / off, 2 and 2 thirds feet on / off, click on / off, slow attack on / off, sustain on / off,sow on / off,fast on / off, vibrato on / off
User setting provides provides another 9 sounds.
Volume setting for Flutes
Special Section for right or left hand
Electric piano, steel guitar, synth brass, piano, jaz guitar, soft brass, syth strings, slow strings,organ, tango accordion, strings, vocal, mussette, master 
Sustain on / off, chorus on / off, octave on / off
User for another 14 sounds
Volume for special section.
Left hand section for Chords
Electric piano, nylon guitar, piano, jazz guitar, soft brass, slow strings, accordion 1, strings, organ, accordion 2
Chorus on / off, sustain on / off, Octave change, Volume controls left hand.
User settings provide 10 further sounds
Bass section 
Bass 8 feet, accordion, organ, acoustic, finger, synth, fretless, slap
Sustain on / off, Octave change
User provides 8 further sounds
Volume change for bass
Rhythm Section 
Drums on / off, Acc1 on / off, acc2 on / off, acc 3 on / off,
Drums volume, acc1 volume, acc2 volume, acc3 volume
Rhythms waltz 2 tango, march 2, foxtrot, showtime. Dixie, rock and roll, waltz, polka, marhc, swing, standard, big band, shuffle, blues, mambo, cha cha, traditional, rock, country 2, dance, disco, bossa, sambo, rhumba, international, country 1, 8 beat, 16 beat, slow rock.
Variation 1, 2, 3
Style bank A, B, C, Automatic set up, start / stop, drum kit, memory, auto bass, auto chord, metronome, intro 1 / ending, fade out, auto / start, fill 1 / intro 2, fill 2, count intro.
Conductor section 
Set, midi, left vol, touch sens, transpose, pitch, magic chord, Orla magic chord, duet, reverb, enhancer, bass accompaniment, left accompaniment, special accompaniment, right 1 accompaniment,. Right 2 accompaniment, special accompaniment, flutes accompaniment
Overall pre sets 
40 on / off presets
Rhythm lock
User style 
User, drums, bass, accompaniment
Disk features 
14 button on / off
Other features 
Digital display, navigator buttons, master volume
Connections 
Midi in 1, midi in 2, midi thru, midi out, switch pedal, volume pedal, switch pedalboard, line in R R+L L, line out R R+L L, Headphones.
With OMC when you play a chord with the left hand a complete chord is added to the right hand (this is a fabulous effect which enables the simulation of multi players from one instrument - my favourite feature).  This setting can be used for close harmony or open harmony configuration. With polyphonic 1, polyphonic 2.
You can also play using the duet setting which adds a second note to the right hand.
This is a summary of some of the main features of the Orla expander which gives thousands of combinations and was built especially for the accordion.  We find it gives a very full sound and we love the musette settings, the automatic harmony additions and especially the spacious sounds.  We also find this unit very easy to use and yet all sections are easily controllable.