You get best results with "iPad Air" or "iPad mini retina" connected to a stereo equipment thru the earphone connector (do not use Bluetooth which has to much delay time). See the "known problems" on the bottom.

This App "Auto Accompanist" has the same features as the popular "Accordion full" (see details there), but includes an amazing new functionality. No external sound module is required (General MIDI sounds are included).
See the first video here: https://www.youtube.com/watch?v=Em5TNB89Gzc

Let you accompany automatically (more than 100 styles included) by pressing a chord key on the bass side of the accordion or play the chords with an external MIDI keyboard (MIDI interface required). Set the chord recognition split point (left/right hand) for the external keyboard in "Settings". For MIDI Out, set MIDI Thru to "ON".
The styles (e.g. Tango, Waltz, March) are based on simple MIDI files (no style files ".STY"!) which you can produce yourself with a sequencer program or e.g. with "Band-in-a-Box" (PG Music Inc.). There are also good compatible styles available for "Band-in-a-Box" from "Norton Music". See the included two sample files, which you can use as base to create new accompaniments.

The MIDI files must comply with the fellowing (channel numeration is 0-15, not 1-16):
- 2 bars drum intro (used only for synchronization)
- 4 bars accompaniment
- 1 or more bars ending
- Channel 9 (10) for drums
- Channel 10 (11) for bass
- Channels 11 to 15 (12 to 16) accompaniment
- MIDI events for instrument, volume, reverb, chorus and left/right must be present, if you will save changes
- Tempo information
- For a "Cmaj" based MIDI file, name it *_Cmaj.mid
- For a "Cmaj7" based MIDI file, name it *_Cmaj7.mid (e.g. "Tango_Cmaj7.mid")
- The MIDI file must be a "Type 0" file (single track).

If you are not able to make a "Type 0" MIDI file (e.g. user of the Mac version "Band-in-a-Box"), please send me the file, I convert it for you.
Changes that you make on existing styles (like tempo, instrument, volume and reverb) can be saved in a new MIDI file for later easy access. The master volume is not saved.
If you need help to create a MIDI file used for accompaniment, please contact me.
As the MIDI files for accompaniment are recorded in "Cmaj" or "Cmaj7", it is possible, that not all 32 detected chords sound as you like it (optimized for the accordion, maj, min, 7 and 7dim). Send me new accompaniment MIDI files, I will put them in a later version.

Tips:
- When you hold down the button "A" and then press "B", then the bars are played alternately (each combination is possible, except "End"). This may be useful for waltz styles like "LUCILLE" to hear the alternating bass.
- You should always press a new chord a little time before the end of the bar to make sound the new chord correctly from beginning.

Known Problems:
- In iOS 7 there is a function called "Multitasking ...". Please set the switch to OFF (in iPad, Settings, General). If you don't do that, playing with multiple fingers does not work correctly!
- Holding down e.g. two buttons on the bass side a long time while playing multiple notes together on the melody side, makes the iPad playing himself unwanted notes. Try to rotate the iPad (180°) to minimize the problem. When the iPad is connected to the Mac (lightning cable) this effect did not happen. This is an iPad touch screen problem.
- Important note if the "MIDI In" does not work:
After changes in the iOS 6 update, it appears that when you launch a new App that uses MIDI, the MIDI device will fall offline, and the only way to reset the connection is to unplug the MIDI device and reconnect while the new App is open.
- Sorry for the sporadic crashes (located in AudioToolbox). Do not use the App on stage. Apple says, that in iOS 7.1 this should be fixed, but this seams not to be the case. Please close the App completely after a crash, before restarting.