Timestretched: audio stretching on the command line

I was recently reminded of the wonders of paulstretch by a 8-fold slowed down version of Pyramid Song by Radiohead.

Slowed down version of Pyramid Song

Paulstretch is an audio manipulation widget that can stretch or compress the time of an audio recording. Note that it doesn’t “slow down” or “speed up” a recording, it resamples the audio and recasts it over a different time scale while maintaining the pitch. There’s lots of examples on the web of how paulstretch can stretch a song, but fewer examples of the other way around. I wondered what time compression would sound like for a slow song.

There’s a plugin for Audacity, which allows stretching but does not allow compressing. There is a python version available to run paulstretch from the command line, and another user has added the ability to process lossless audio (in FLAC format). My fork is here (with a very minor change) for permanence. These scripts all allow time compression as well as time stretching.

I compressed Ebony Tears by Cathedral. A doom metal tune from 1991 which is at ~56 bpm. Two-fold compression (-s 0.5 with 0.25 sampling) recasts the song as a 112 bpm heavy metal tune.

Ebony Tears twice as fast

For a more well known example of a slow song, I went for “Last Night I Dreamt That Somebody Loved Me” by The Smiths. Compression works OK with this song. Without sounding like a total philistine, the intro with the animal noises and Johnny Marr plonking away on the piano becomes mercifully shortened. Then the main song (0:58) turns into a more jolly reel at 0.5 compression.

Last night… twice as fast

…and a somehow more urgent moody tune (at 1:28) with 0.75. Disclaimer: I love the original version of this song, at the correct pace. I am not saying this is an improvement in any way.

Last night… 1.5 times as fast

Compressing songs was fun, but somehow not as fascinating as stretching. The trick is to pick songs with minimal percussion and vocals for the stretched version to sound like something other than prolonged noise. Here is a four-fold stretch of Into The Groove by Madonna. The vocals are OK but those gated 80s drums sound awful smudged over a longer time window.

Intooo the grooooove

And here are two-fold and four-fold versions of Joe Satriani’s instrumental The Forgotten (Part One). The original is an agitated guitar workout. It is transformed into an ambient soundscape with stretching.

The Forgotten x2
The Forgotten x4

The command line versions of paulstretch are easy to use and fun to experiment with. Feel free to comment with suggestions for good contenders for stretching or compressing.

The post title comes from “Timestretched” by The Divine Comedy from their Regeneration LP.

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