An open-source audio time-stretching tool for Windows

v1.03 - December 28th 2007


BestPractice is a musician's practice tool, to slow down or speed up music, either from an MP3 file or directly from a CD. Ordinarily the sound is distorted when slowed down our sped up - you get the effect like when playing a 33 rpm record on 45 rpm speed (remember the Chipmunks?). BestPractice tries to correct this, so you can slow down and speed up music, while keeping the original pitch. It is also possible to change the pitch of the music without affecting its tempo. Play along with for instance Eb tuned guitars without retuning your own, or slow down that high-speed guitar solo on a CD that you like to learn.


Small screenshot

This splits up in two parts: "why is BestPractice made?" and "why would I use it?"
To start with the first: I saw that there were programs available on the internet that do this, and you have to pay for them ($20 to $50). Since I thought: 'I can do that', I had to prove it, right?

And for part two - well, there are probably more reasons, but those I can think of are:


You can find the installer for BestPractice here (652 kb). Please consider a donation if you find BestPractice useful; already just a few dollars is very much appreciated! See Donations or donate using your cell phone.

The source code can be found here.
Note that the cd ripping library used by BestPractice, akrip32, is licensed under the LGPL and the full source code is available from You do not need to download this to use BestPractice.


BestPractice can be translated quite easily to (almost) any language. The amount of work for the program itself is limited to translating ~72 lines, where a line is a few words at max. The translations are created from a text file, with '.po' as extension. I use a program called poEdit (freeware,, which makes editing a bit easier, though any text editor capable of saving unformatted plain text files will do (like notepad). A template to modify to your own language you can find here (zipped, the dutch version) If you need any help or explanation, feel free to ask me. Or, if you see errors for your language, please contact me to correct this.

Languages already provided by users:

To do

There are still a lot of things to do, have a look here for details:
Source Forge task list


No CD players found

On Windows XP/2000, the cd ripping library uses the SCSI passthrough interface. For some set-ups, mostly involving burners or virtual drives, no CD players or not all CD players are found. If this is the case, get the file wnaspi32.dll provided by Ahead Software AG from here. Download this file and place it in the program folder of BestPractice. Often the problem is then solved.
In case you're wondering, due to the license I cannot include a copy of this dll with the program (as far as I know).

BestPractice crashes

on Windows 98:
If only I knew what is going on... But I don't, so no solution available yet. Please do keep the crash reports coming, one day I'll figure it out. Two suggestions:

On XP or Vista
Sometimes this is caused by the absence of any CD player. Though BestPractice shouldn't care, apparently the cd reading library doesn't behave well on some computer/windows combinations. As a workaround, you can install a virtual cd drive, such as Daemon Tools.
Running BestPractice as restricted user

This needs some preparations (thanks to Matthias L., and I quote):
"it looks as if the problem is solved. Nero didn´t find any CD writer on the machine. This happens if the current user has restricted rights. Ahead software provides a tool called "Nero BurnRights" to fix this. After using this tool, BestPractice works fine (as does Nero, of course :). One little trick remains: on exit, your software tries to write to bpsettings.ini. So one has to adjust the rights of this file, or - at first - generate it via a run of BestPractice as an admin (then the file can be created)."

Please report other problems on the forum.

Should you happen to like BestPractice, then a nice e-mail is always very much appreciated. Should you happen to like BestPractice even more, a small donation as a way to say thank you is most welcome. You can either donate through PayPal (no account needed when using a credit card):

Or, you can ask me for my snail mail address and stick to the old-fashioned envelope+cash system.


You can contact me (Robert Moerland) at


Version 1.03

Version 1.02

Version 1.01

Version 1.00

Version 0.99-0.1
These are stripped from the web site. See the included help file for details

Note: the real Celine Dion was not hurt during the creation and testing of this application.