Qtractor is an audio/MIDI multi-track sequencer application written in C++ with the Qt4 framework [1]. Target platform is Linux, where the Jack Audio Connection Kit (JACK) for audio [2] and the Advanced Linux Sound Architecture (ALSA) for MIDI [3] are the main infrastructures to evolve as a fairly-featured Linux desktop audio workstation GUI, specially dedicated to the personal home-studio.

Features:

• Multi-track audio and MIDI sequencing and recording.
• Developed on pure Qt4 C++ application framework [1] (no Qt3 nor KDE dependencies).
• Uses JACK [2] for audio and ALSA [3] sequencer for MIDI as multimedia infrastructures.
• Traditional multi-track tape recorder control paradigm.
• Audio file formats support: OGG (via libvorbis [6]), MP3 (via libmad [7], playback only), WAV, FLAC, AIFF and many, many more (via linsndfile [4]).
• Standard MIDI files support (format 0 and 1).
• Non-destructive, non-linear editing.
• Unlimited number of tracks per session/project.
• Unlimited number of overlapping clips per track.
• XML encoded session/project description files (SDI).
• Point-and-click, multi-select, drag-and-drop interaction (drag, move,drop, cut, copy, paste, delete, split)
• Unlimited undo/redo.
• Built-in mixer and monitor controls.
• Built-in connection patchbay control and persistence (a-la QjackCtl [13]).
• LADSPA [5], DSSI [11] and native VSTi [12] plug-ins support.
• Unlimited number of plug-ins per track or bus.
• Plug-in presets, programs and chunk/configurations support.
• Audio/MIDI clip fade-in/out (linear, quadratic, cubic).
• Audio clip time-stretching (WSOLA-like or via librubberband [9]), pitch-shifting (via librubberband [9]) and seemless sample-rate conversion (via libsamplerate [8]).
• Audio/MIDI track export (mix-down, merge).
• Audio/MIDI metronome bar/beat clicks.
• MIDI clip editor (piano roll).
• MIDI instrument definitions (a-la Cakewalk(tm) [15])
• JACK transport sync master.
• MMC control surface enabled.
• Configurable keyboard shortcuts.

New in v0.2.1

• Gradient eye-candy (NEW)
• DSSI multi-instance plug-in issue fixed
• Clip waveform/piano-roll rendered while recording (NEW)
• MIDI pitch-bend, omni-channel filtering and recording fixes
• Play-head positioning in the thumb-view (NEW)