REAPER (Rapid Environment for Audio Prototyping and Efficient Recording) is designed for the recording, arrangement, editing, mixing and rendering of audio.

Basic features:

• Support for an unlimited number of audio tracks.
• Audio tracks are all fully routable (multiple inputs, outputs).
• Volume, pan controls and envelopes per track.
• Supports audio processing plug-ins (DirectX, DXi, VST, VSTi, and Jesusonic) with automation, easy chain manipulation and editing.
• Pitch shifting and time stretching.
• Fast, reasonable and usable Windows-style UI, working well on both low and high resolutions or multiple monitors.
• ASIO, Kernel Streaming, WaveOut, and DirectSound support for playback and recording.
• Reads WAV, OGG, MP3 and MIDI files, records WAV and MIDI files.
• Can render to WAV, OGG, MP3 if lame is installed.
• Full SMP support (can utilize 2 or more processors).
• Multi-layer undo/redo support.
• User creatable color themes.

Advanced features:

• Unlimited send/receives per track, with configurable parameters (pre-fx, post-fx, volume/pan adjustment/envelopes, mix to mono, phase, etc.).
• Any track can act as a bus, for routing flexibility.
• Tracks can have one or more (mono or stereo) hardware sends, for analog mixing capability.
• Fully routable/FX-able folder tracks that can contain group tracks.
• Item grouping.
• Ripple editing.
• Grid/snap support with configurable options.
• Markers.
• Unlimited takes per media item.
• Auto punch-in/punch-out functionality.
• Automatic record monitoring modes.
• Selection length granularity options as well as grid snapping.
• Tempo envelope (for grid lines/snapping/ruler), play-speed envelope.
• Project consolidation/export options (for rendering all or parts of any number of tracks to WAV, etc.).
• A UI and architecture that allows you to easily cut loops of many tracks simultaneously, without having to write them to disk.
• Support for plug-in generated media (such as click tracks, etc.).
• Project tempo envelopes for variable tempos in track, grid/snapping that supports variable tempos.
• 64-bit floating point sample pipeline for high quality.
• Advanced recording and monitoring options; examples:
  • You can route multiple tracks (inputs and/or media items) into a bus, and record THAT mixed down version.
  • You can record the input signal, or record the post-FX, post-track-render signal.
  • You can switch recording sources on the fly, even while recording.
  • You can arm/disarm tracks' inputs while playing or recording.

Other features:

• Human readable, human editable, backwards and forwards compatible project file format.
• Options to build peaks for recorded files on the fly.
• Lots of control for the user to specify where recorded files go, etc., when dealing with many projects.
• Template support to make it easy to load a project template and save it as a new project when you begin.
• Input/output channel name aliasing (why view your inputs as "MOTU 896: Analog 1" when you could have them be "Vocal Mic", etc.).
• Options for automatically backing up project files to alternate paths, time-stamped versions, etc.