iReal Book app has been around since the beginning of the App Store. The app provides the chord changes for all the tunes in the classic Real Book (plus hundreds more!); the app does not, however, provide the head (melody). A massive update to the app last week takes this app from interesting and possibly useful to a must-buy. The developer has added a Band-in-a-Box like player. You can now use the app to improv to all 900 charts using the built-in MIDI playback. The app also allows you to easily create your own tunes by entering the chord changes. The MIDI is a little square compared to a live group or even an Aebersold (as these are recorded by real musicians), but it is a great tool for those with an interest in improvisation.

Pros:

• Universal iOS app. Works natively for iPhone, iPod Touch, and iPad.
• Over 900 tracks
• You can build your own charts
• The tempo and key of each chart are adjustable
• Choose different styles for each chart (i.e. switch to latin or swing, etc) with in-app purchase of $5.99 jazz styles pack
• You can change the EQ levels of each instrument
• Search by track name, composer, style, and create playlists
• Built in forum for iReal Book users
• Supports multi-tasking in iOS 4+

Cons:

• The app is $9.99, so it is on the spendy side of apps, but it is a very polished and complete app.
• Jazz Styles Pack is an additional $5.99 via in-app purchase, bringing the app to $15.98 for the full-featured app
• No heads. This is understandable though, as the melodies are copyright protected
• While multi-tasking is supported, it does not use the music player API, so you can not start and stop the playback from the main music controls. You have to relaunch the app to stop playback, or double-click the home button and kill the app.