Live Looping is the recording and playback of a piece of music in realtime.
Since 2007 there are multitrack loopers that allow you to repeatedly record and layer sounds into multiple tracks.
For example. you create 3 stereo loops running in sync, which then can be turned on and off individually, while being able to perform live simultaneously.
This way, in combination with effect pedals, you can arrange complete songs in realtime.
In the past plenty of music equipment was needed and additionally either power connection or home-made battery solutions.
Considering that, the Boss RC-505 loop station with its 5 stereo loops is a good all-in-one solution, despite its need for 9V power.
It offers quiet a few internal effects before and after the looping section, and some of the stutter and pitch effects can even be applied to single loops in hindsight.
However live looping on a studio level with a mic or instrument also requires standard audio effects like EQ, gate/expander, compressor, limiter.
Here Ableton Live on a macbook or a surface tablet (with an audio interface and a controller) is a very good solution.
But there's a more mobile solution, powered by USB battery packs: An iPhone with an audio interface!
But to get started just an iPhone, a headset and these three apps are needed: Tonestack 3, Loopy HD and Audiobus 3.
Loopy is a live looping app and Tonestack is a multi-effects app (originally built for e-guitar/bass, but also working great with other sources like vocals etc.
In Audiobus Tonestack gets connected to Loopy by choosing Tonestack as source and Loopy as target.
To connect a microphone and speakers you'll need an audio interface like the Zoom U-22 for example.
I use a DPA 4099 mic and two Dockin' D-Fine speakers in stereo mode.
Then I send the signal through a Korg Mini Kaoss Pad 2, a multi-effects tool with touchpad control.
After all I also use the following apps to fatten the signal a little:
DDMF 6144 Equalizer, DDMF NYCompressor and DDMF NoLimits Limiter.
Occasionally used songs in street performances (by genre):