Monitoring / Fold-down

Monitoring and format tools audition, inspect, or adapt ordinary multichannel tracks without converting them to ambisonics. Use a fold-down for a narrower stereo or quad monitor path, Matrix Upmix for a larger direct speaker format, and a passthrough meter when the original channel layout must remain available downstream.

For a format-first overview that also covers ambisonic Stereo and Head decoders, see Listening on a Stereo System.

Workflow

Choose a stereo or quad fold-down for listening, or Analyzer Meter when the wide bus must pass through unchanged; configure the REAPER track and plugin pins, then set the fold-down input count or meter WIDTH.
Route the stereo, quad, or passthrough output to the intended main speaker or monitor destination, then begin playback.
For a fold-down, set the layout, weighting, and autogain; for the meter, choose the display view.
Confirm that unused lanes are silent where the bus narrows and that the destination receives only the intended outputs.

Fold-down Plugins

Output Autogain Stereo: accepts as many as 128 input channels and produces a true stereo output with automatic energy management and 3D placement controls.
Output Autogain Quad: produces L, R, RB, and LB quad output from a wide source track.

Format Expansion

Matrix Upmix 64 adapts a named input format to an equal or larger named output using an exact positive-gain input/output matrix, a contained stereo-difference strategy, practical upmix presets, AED coordinates, and a Tier Rings layout. It is the non-ambisonic counterpart to fold-down: a deterministic channel distributor rather than a sound-field encoder.

Metering

Analyzer Meter 64 is a fixed-width passthrough meter with channel-grid, spatial-layout, and energy-over-time views. It is the better choice when the monitor display must not collapse the bus.

Host Routing

The stereo and quad tools expose narrower output buses. In REAPER, inspect the plugin pin connector and enable Zero out unmapped output channels when unused track channels would otherwise pass around a fold-down plugin.