Digitron patches together the way modular synths work — drag a virtual cable from an LFO’s output to a filter’s cutoff input, and the connection actually does something — without needing real hardware or MIDI cables. It runs 8 tracks with individual mixing and panning, records and edits audio in place, and supports Audio Unit v3 so it can host or be hosted by other iOS synth apps. Free to download, with optional in-app purchases.