GarageBand consists of a pro-quality musical instrument and recording studio. This is not a “niche thing”, as surveys show that 50% off all households in the US have at least one person who plays an instrument.
You can digitally mix up to 64 tracks, play up to 50 digital software instruments and use up to 1000 pro-quality loops. There are 200 audio effects and even vintage guitar amp sounds.
Play any USB or MIDI instrument or keyboard and live record your music over any pre-recorded loops. Then save the resulting composition to iTunes and even export it to your iPod!
This software comes bundled with iLife and is on sale for $49.