The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Matthew Curtner:
Intonation Lite is the free limited version that allows you to tune guitar or bass guitar using your iPhone, iPod Touch, or iPad.With a realistic guitar interface and easy to select tunings, you can quickly and easily tune your guitar and begin playing.