Editing Tempo of MP3 Audio Files

[mikebel]

I am currently using a PC Platform with Windows XP and Audio Unstable 1.3.6 installed. I would like to be able to change the tempo of MP3 Audio files < +/- 8% to be used for ballroom/country western dances. However, after editing a file, the tempo changed as advertised, but I noticed some distortion (fluttering, harmonics, etc) in the instrumental portion of the audio track. This appears to happen at all BPM ranges. For example, I wanted to increase the tempo of "You Light Up My Life" by Debbie Boon, which is currently at 78 BPM, to 84 BPM. Additionally, I wanted to decrease the tempo of "Forever and Ever, Amen" by Randy Travis from 180 BPM to 175 BPM. In both cases, the fluttering/harmonic distortion made the piece of music unusable. Is there anyway that I can mitigate or eliminate this effect when I change the BPM of MP3 Audio Files?

[steve]

The problem may be with the way that changing the tempo is done. Audacity has to cut up the music into tiny little pieces and either space out the pieces to make the tempo slower, or cut bits out to make the tempo quicker. If you are only changing the tempo by 4 or 5%, then you should find that it does it quite well, but once you get over around 10% tempo change the distortion starts to become quite noticeable. You can try using the "Change Speed" instead of the "Change Tempo" - that will give you better sound quality, but a change in the pitch (like a record playing at the wrong speed). If you are already using the "Change Speed" effect, then no there isn't anything that you can do about it because the fault is due the audio file, and not to do with the software.