The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Chris Wolfe:
YUMI:synth is the worlds first realistic sounding bowed string simulator for iOS. All sound generation is completely synthesized, absolutely no samples are used.You can play two strings at once (at different locations on the scale) and bow manually or automatically. The scale system allows you to quickly define all the playable notes.Also included are two high quality stereo effect units: ping-pong delay and reverb.You can easily save/load presets, and backup your presets via iTunes.To play in Manual mode, touch a string (purple or blue box) while sliding your finger on the bow (yellow box). In Auto mode, the bow slider turns into a slider controlling the volume.The control under each string allows you to move/zoom your current view of the scale.