Is there any way to change tempo without distortion?

I have a music WAV with two chords in it, and the second chord needs to be four times the duration of the first. The original recording is close but not quite there. So I tried Change Tempo from the Effect menu. I shortened the first chord by 50% and lengthened the second one by about 20%. Now they both sound distorted. The online manual says distortion will occur if you make “extreme” tempo changes. I’m frustrated that only 20% apparently is extreme.

Can someone advise me as to a better way to do this so I don’t waste more time?

Try the Sliding Time Scale / Pitch Shift… effect
If the notes start or end at non-silence then you may need to copy the notes to another track so that you can edit a short cross-fade so as to avoid clicks at the transitions.

Thanks, Steve, I never realized how much better the Sliding Time Scale/Pitch Shift is.
I’ve also used this external app for extreme tempo change:

It’s a shame about the glitch that it creates at the start of the selection, but that has been fixed in the next version of Audacity (2.0.1 or whatever).

Thanks; I’ll give that a try!