MidiBand converts an iPhone/iPad connected to a General MIDI synthesizer keyboard into a universal accompaniment machine, with thousands of styles available from the Web. The app replicates and expands on the auto-accompaniment feature of common musical keyboards by playing Intro/Verse/Chorus/FillIn/Ending loops from widely available Style files (.sty) over a MIDI interface. It establishes a two-way CoreMIDI connection between the iPhone/iPad and your synth, analyzes chords played with your left hand, and sends the style's accompaniment in the key of the chord back to the synth. At the same time, the melody/voice part can be played through the app with your right hand.
As a bonus and one of its key features, with a few clicks MidiBand can convert standard MIDI files for popular songs into your own styles, letting you play your favorite songs and sound just like the original - all in no time.

A free MidiBandFree app, also in the App Store, showcases the MidiBand features. In addition to the features of the free app, the paid MidiBand app:
* Can convert both Type 0 and Type 1 MIDI songs into your own custom styles
* Features iOS 7 interface
* Connects to other music apps via Virtual MIDI
* Supports up to 12 accompaniment sections instead of 6 in MidiBandFree
* Lets you select any voice for the right-hand melody play
* Allows you to rename created styles
* Lets you assign hardware MIDI knobs/buttons to control volume and start/stop the playback.
The MidiBandFree app also lets you test your MIDI setup and connections - that everything works as expected. The connectivity features and the playback engine in the MidiBandFree and MidiBand apps are identical; so if the free app works in your particular MIDI setup, the paid app will too. 

The MidiBand app by itself produces no sound from the iPhone/iPad speakers; it will only work in conjunction with a Virtual MIDI synthesizer app or a General MIDI hardware synth for playback. Since the MidiBand app must in any case be connected to a MIDI keyboard for changing chords, that keyboard usually can play back your MIDI. If you do not own a General MIDI-capable keyboard, this app is not for you.

When connecting the MIDI keyboard to MidiBand, you are not limited to iPhone/iPad hardware MIDI add-on devices such as iRig or MIDI Mobilizer. If you own a Mac, you can physically connect the MIDI keyboard to a Mac via USB and then setup a wireless session between the iPhone/iPad and the Mac using Audio MIDI Setup application for OS X - and MidiBand will work with that.