REAPER is a powerful but sensible Windows application that lets you record, arrange, edit, and render multi-track waveform audio. It provides an extensive set of features, but is a very small and lightweight application (the installer is less than 1 megabyte, and includes many effects and a sample project). REAPER supports ASIO, Kernel Streaming, WaveOut, and DirectSound for playback and recording. It reads WAV, OGG, and MP3 files, and records WAV files. You can arrange any number of items in any number of tracks and use audio processing plug-ins (DirectX and Jesusonic). REAPER also supports volume, pan controls and envelopes per track, multi-layer undo/redo, and user creatable color themes.

Basic features:
- Portable - supports running from USB keys or other removable media
- 64 bit audio engine
- Excellent low-latency performance
- Multiprocessor capable
- Direct multi-track recording to many formats including WAV/BWF/W64, AIFF, WavPack, FLAC, OGG, and MIDI.
- Extremely flexible routing
- Fast, tool-less editing
- Supports a wide range of hardware (nearly any audio interface, outboard hardware, many control surfaces)
- Support for VST, VSTi, DX, DXi effects
- ReaPlugs: high quality 64 bit effect suite
- Tightly coded - installer is just over 2MB

Editing features:
- Tool-less mouse interface -- spend less time clicking
- Drag and drop files to instantly import them into a project
- Support for mixing any combination of file type/samplerate/bit depth on each track
- Easily split, move, and resize items
- Each item has easily manipulated fades and volume
- Tab to transient support
- Configurable and editable automatic crossfading of overlapping items
- Per-item pitch shift and time stretch
- Arbitrary item grouping
- Markers and envelopes can be moved in logical sync with editing operations
- Ripple editing - moving/deletion of items can optionally affect later items
- Multiple tempos and time signatures per project
- Ability to define and edit project via regions
- Automation envelopes

Changes in REAPER 3.3 - February 10, 2010:
* Action: write current value on envelopes from edit cursors to start/end of project
* Action: unarm all envelopes
* Action: write current value to time selection on all armed, write-enabled envelopes