Rubber Ring is a tool for practicing song parts. Pick an audio file, mark a start/stop region on its waveform, and play it back in a seamless, gapless loop. It auto-detects tempo and beats to snap the loop markers to a beat grid, with full manual override. Early-stage release — expect rough edges. Feedback and bug reports welcome via Issues. Features: * Import-and-own library — picked files are copied into app-private storage, so loops never break when the original is moved, renamed, or deleted. * Waveform region selection with gapless looping — drag start/stop handles to mark a section; the loop boundary wraps with zero audible gap or click. * Automatic, hand-editable beat grid — a dependency-free estimator finds BPM and a downbeat, and handles snap to the beat grid. * Chord detection with a hand-editable chord lane — chords are labelled over the waveform; tap to relabel, split or merge. Detection is tuned to the author's own material, so the lane is there to correct by hand, and can be turned off. * Per-track audio normalization — boost a track that was mixed too quietly, by peak or by loudness; your original file is never altered. * Adjustable playback speed — slow a tricky passage down (or speed it up) without changing pitch. * Count-in — long-press Play to start after a metronome counts you in at the track's tempo. * Saved loops and practice arrangements — capture named sections per track and chain them into a sequence, each repeated as many times as you set. * Backup & restore — export your whole library to a file and restore it after a reinstall. * English and German, with optional German note names (H and B) for chords. * Opens audio shared from other apps. No ads, no trackers, no network access.