According to zee at the Intua Beatmaker Discussion Forum, 2nd Gen iPod Touch Music Producers can record and sample audio (even Phantom Powered mics ?!?!?) into Beatmaker.
He states that “you’re NOT restricted to crappy headset mics!”
He instructs that you first attach (to your 2nd Gen iPod Touch) a Belkin AV Cable as shown below:

This cable has 3 [...]

If the Roland SP-555 sampler is in your toolbox and you want to sample and loop from various input sources such as a CD Player, MIC or turntable, you can use the Loop Capture function. Check out this video demonstration in which a CD Player is connected, recorded and looped during playing as well as [...]