All mutations run on the control thread through the existing stop, history and
prepared-plan workflow. No new dependencies are required.
## Phase 58 — Persistent Arrangement Markers
Edit/Markers/Set at cursor adds or renames a marker; Remove at cursor removes the exact tick key. Markers draw names and vertical guides in the arrangement and survive project save/load and undo. Up to 128 markers are supported. Names may overlap visually when markers are close; markers do not change playback by themselves.
View/Previous marker and Next marker navigate without wrapping and stop playback before seeking. Loop current section uses the last marker at or before the cursor through its successor; the final section ends at the final clip endpoint. Empty final sections reject. Loop ranges remain existing UI preferences rather than marker metadata.
Edit/Time inserts a gap or removes a tick range beginning at the cursor. Clips crossing either edit boundary reject the entire operation; split them first. Contained clips and their notes are removed; later clips, markers and absolute automation points shift together. Source notes within retained clips do not move. No interpolation guard points are generated, so automation ramps across the boundary may change slope. Loop preferences are unchanged.
Edit/Duplicate complete track copies the selected non-bus track adjacent to its source. Clips, notes, instrument settings, static mix, bus routing and mixer automation are independent model copies with fresh IDs; WAV references remain shared. The modular graph and live-input target are unchanged. Bus duplication is rejected. Capacity errors leave the original document unchanged.
The existing Split clip at cursor command (S) now handles MIDI as well as audio. Left retains its ID; right gets fresh IDs, the same source content and an adjusted source offset. Hidden notes remain editable. Split is nondestructive, but instrument note envelopes may retrigger at the new boundary; original sine rendering retains source phase. Capacity failures preserve the project.
Edit/Consolidate MIDI clips merges two or more selected MIDI clips on one track. The new clip spans their full bounding range; gaps and overlapping notes remain. Notes outside visible trims are discarded and crossing notes are cropped to audible boundaries. IDs are fresh. Cropped notes start anew, so envelope/phase behavior can change. Audio or cross-track selections reject atomically.
Edit/MIDI tools/Humanize applies timing variation up to 960 ticks and velocity variation up to 127, using a 32-bit seed and stable note IDs. Repeating from the same original state reproduces results; applying repeatedly accumulates edits. All source notes are affected, including hidden trimmed notes. Timing outside source bounds rejects the entire edit; velocities clamp to 1..127. This is offline editing, not live randomness.
Edit/MIDI tools/Build chords accepts 1..8 unique nonzero semitone intervals, such as 4 7 for a major triad or 3 7 for minor. Originals remain; added notes copy timing, velocity and channel. Negative intervals support lower voicings. All source notes are processed, including hidden trimmed notes. Pitch overflow or capacity rejects the whole operation; existing unisons are not deduplicated.
Edit/MIDI tools/Generate arpeggio replaces source notes with a written pattern. Equal-onset notes on the same channel form a chord lasting until its longest note end. The pattern cycles sorted pitches upward or downward, with the selected step and gate. Each step inherits its chosen note velocity/channel. All source notes, including hidden trimmed notes, participate. This is offline generation with undo, not a live arpeggiator or tempo-synced MIDI effect.
