Steve Lacy used an iRig with his iPhone setup to connect his guitar. More precisely, iRig is an audio-interface adapter rather than a conventional software plug-in: it lets an instrument send its signal into a phone or tablet for recording and processing.
That small connection was central to Lacy’s portable production method. He could plug his guitar into the iRig, route the sound into GarageBand, and build parts without an amplifier, mixing desk, or full studio. The setup gave him a practical way to capture guitar and bass ideas wherever he was, while the iPhone’s microphone handled vocals.
The answer is sometimes confused with AmpliTube or Guitar Rig, which are software effects and amp-modeling platforms associated with guitar recording. Those tools can process guitar tones, but iRig is the hardware interface Lacy used to connect the instrument to his phone. His celebrated phone-made recordings later helped establish his reputation as an inventive producer.