Change the speed of any song, without the chipmunk

How changing tempo works

What happens when you change tempo

Slowing a record down on a turntable makes it lower as well as slower, because both are the same physical change: fewer samples per second. A time-stretch does something harder. It cuts the audio into short overlapping grains, spreads them further apart in time, and rebuilds the gaps so the result runs longer while every note stays on the same pitch. Speeding up is the same idea in reverse.

That is why the tempo control here does not turn a singer into a bass. The song runs at 80% or 120% of its original speed and the key is untouched.

Practising an instrument at reduced speed

This is the most common reason people slow music down. A fast run stops being a blur at 70% and becomes a sequence you can actually hear note by note. Because the key does not move, what you learn at 70% transfers straight to playing along at 100% — you are not retraining your ear to the wrong notes.

Work up in steps. Learn the phrase at 60-70%, then 85%, then full speed. Dropping straight from 60% to 100% usually undoes the practice.

Why heavy slowdown starts to sound strange

Time-stretching has to invent the material that fills the extra time, and the further you stretch, the more of the result is invention. Sustained sounds — voice, strings, pads — hold up well because they genuinely do continue. Sharp transients do not: a drum hit is a single event a few milliseconds long, and stretching can smear it into a soft thud or repeat it faintly.

Below about 50% most material starts to show this. It is a property of time-stretching, not of any one tool.

Tempo and pitch are separate here

Because the two controls are independent, you can combine them deliberately. Slow the tempo and leave pitch alone for practice. Slow the tempo and drop the pitch for the slowed-down sound used in remixes. Raise the tempo without raising pitch to tighten a podcast without making the speaker sound comical.