Swap the audio inside an iZotope RX session document

RX has no feature for replacing the source audio in a saved session. When a revised mix arrives, the edits in the session belong to the previous file.

This tool reads the session, substitutes the new audio, and writes a new document with the markers and view state intact. The source document is never modified: every operation produces a new file.

Each edit exists in the file twice: the input RX started from, and the output it produced. From those two, the tool recovers the operation as a transfer function in the frequency domain, then applies it to the corresponding range of the new audio.

This covers fades, gain moves, EQ, and quasi-linear dynamic operations such as de-essing. It transfers where the new audio is a different mix of the same material.

Spectral repair and pitch shift depend on the input in ways a transfer function does not capture. RX does not store enough about an ad-hoc edit to reconstruct one by any means, so this is a limit of the format rather than of the tool.

Where an edit cannot be recovered, it is reported and dropped rather than approximated.

Holding any waveform plays it from the point held. The output lane is rendered by the same code that writes the file.

Where the new audio is a different length, the alignment panel detects the offset and allows it to be adjusted, with a null test for checking the result by ear.

Without a licence key the app opens sessions, shows the reconstruction and plays it back, but does not write the updated document. There is no time limit and no expiry. Entering a key unlocks writing.