GarageBand is one of the most popular app which transforms your device into a collection of Touch Instruments and allows you to create music and podcasts. GarageBand was previously available for iPad only but now it has been launched to both iPhone and iPod Touch devices.
From App store
GarageBand turns your iPad, iPhone and iPod touch into a collection of Touch Instruments and a full-featured recording studio — so you can make music anywhere you go. Use Multi-Touch gestures to play pianos, organs, guitars, drums, and basses. They sound and play like their counterparts, but let you do things you could never do on a real instrument. Enjoy a full range of Smart Instruments that make you sound like a pro — even if you’ve never played a note before. Plug an electric guitar into your iPad, iPhone or iPod touch and play through classic amps and stompbox effects. Use the built-in microphone or a guitar to record, or capture any performance. Then mix up to eight tracks to create a song you can share.
GarageBand will provide following salient features
• Universal app designed for iPad, iPhone, and iPod touch
• Create custom chords for Smart Instruments
• Support for 3/4 and 6/8 time signatures
• Reset song key without transposing original recordings
• Transpose songs in semitones or full octaves
• Additional quantization options for recordings including, straight, triplet and swing
• New audio export quality settings for AAC and AIFF (Uncompressed)
• Arpeggiator available in Smart Keyboard
• Adjustable velocity settings for Touch Instruments
• Numerous enhancements, including automatic fade out and improved audio import options
GarageBand can be downloaded from App Store which is available at a price tag of $4.99. It is compatible with Compatible with iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation), iPod touch (4th generation) and iPad running iOS 4.3 or later.