I have been using Band in a Box for 10 years, since my Berklee days. It is the best tool for practicing over chord changes and developing improvisational skills on any instrument. The new version with the "Real Drums" and "Real Styles" is amazing. Bye-bye to cheezy MIDI rhythm sections, these are real players and they are much more inspiring to jam along with. I recommend this to EVERY musician!
Band in Box 2013 Megapak
This is the single best music purchase that I have ever made. There is no beating this as a practice tool, even with all the youtube backing tracks available.
Being able to make you own progression or just practicing over a single chord. It takes moments to create.
Get the Megapak because the extra real tracks or well worth it. Sweetwater had the best price online for this package.
A bit dizzying, but pretty cool
I am a 47 year old software engineer with no music software background at all. I'm beginning to gig out and wanted to make some drum and bass backing tracks, load them onto an mp3 player, and route that through the small mixer I use.
These pieces of software are dizzying in their capability AND in their organization and user interface - though the most used features are pretty obvious, there's a ton beneath the surface. I was able to create some pretty groovy stuff in about 5-6 hours. In fact, the absolutely brain dead interface which has become a Windows 7 standard for mp3 players gobbled up more time than BIAB.