In GarageBand, is it possible to change the key at any given point in the timeline?

IIs there a key slider in GB for iPad?

In GarageBand for iPad you can transpose tracks using the mixer controls. If you transpose a track, it will apply to the complete section.

For your blue grass backing track create 8-bar song sections, then you can transpose each section to a different key. See this help page:

http://help.apple.com/garageband/ipad/2.0/index.html#chs175dc411

Transpose regions in the track

You can change the pitch of (or transpose) recordings or loops in a track up or down by semitones or octaves. After you turn on transposition for a track, any new recordings or loops you add to the track are also transposed.

1. Tap Transposition.
2. To transpose by octaves, tap the Octaves up or down arrow, or swipe vertically to transpose by multiple octaves.
3. To transpose by semitones, tap the Semitones up or down arrow, or swipe vertically to transpose by multiple semitones.

Transposition applies to all regions in the track for the current song section, but you can choose different transposition values for the same track for different song sections. If you move or copy a region to a different section with a different transposition value, the value appears as Multiple. For more information about song sections and transposition, see Extend a song with song sections.

You lost me at Tap Transpose. I have the mixer controls open, but I don't see Transpose. I see mute, solo, track volume, track pan, echo level, reverb level, quantization, merge recordings, master effects. Am I at the right place?

Wait, if I add a piano, then the mixer controls have a transpose control. Is the difference the piano is a "touch" instrument and transpose is available only for touch instruments?

What I have now is one time through verse and chorus in A with Smart acoustic guitar, a smart bass line, two percussion lines, and two audio recording lines. I just doubled the song length for a second time through in C. Copied the percussion, acoustic guitar, and bass lines to the new sections. Hoped I could move the guitar and bass up to C, then record new audio in C. But maybe I will have to start new tracks for guitar and bass, edit the chords enough that I can get the four chords I need and lay them down anew.