The Best Free Online Key and
Tempo Change Service 2019

Applications that change key and/or tempo have been around for at least 15 years. There are a number of good paid software programs or applications that perform this function. However, here are also a number of free, online services that can also do this.

By conducting a thorough search on the internet we have identified the websites that offer these services and performed a side by side comparision test. For purposes of our testing we used a file with organ music on which key and tempo was changed. Organ music was used because it has the largest frequency range of ANY instrument. As such it is the most difficult type of music to work with and therefore it will be the first to show distortion when key or tempo is changed.

In rating these sites sound quality AFTER key and/or tempo changes was ranked as the most important. The results of review of these free sites appears below:

Song Surgeon Twisted Wave Conversion-Tool Audio Speed
Audio Trimmer True Tone Online Tone
Voice Changer
Overall Rating
Audio Quality Rating 5 4 4 3.5 3 3 3 N/A
User-Friendly Rating 4 3 3 4 4 4 3 N/A
Converted File Size(from 3.6mb original file) 3.4 mb 4.35 mb 5.8 mb 5.8 mb 4 mb No download Download Failed N/A
Steps to Process 3 5 or more 4 4 4 4 4 N/A
Tempo Change Yes Yes Yes Yes Yes Yes No N/A
Key Change Yes Yes Yes Yes Yes Yes Yes N/A
Upload File Yes Yes Yes Yes Yes Yes Yes N/A
From URL No Yes Yes Yes No No No N/A
Use Microphone No No No No No No No Yes
Playback Preview Yes Yes No No No Yes Yes N/A
Login Required Yes No No No No No No N/A
Multiple Formats Yes Yes Yes Yes Yes No No N/A
Sponsored Ads No No Yes Yes Yes Yes Yes No
Downloadable File Yes Yes Yes Yes Yes No Yes N/A
Intuitive Service Yes Yes No Yes Yes Yes No N/A
1. Song Surgeon

Song Surgeon was ranked #1 because with a 2 half step change there was NO distortion introduced into the file. Beyond this, the online tool is easy to use. It allows you to change both Key and Tempo - and it allows you to change this in whole units - or in smaller increments, should that be necessary.

The step by step process allows you to preview your changes prior to processing your file. This allows hear the key or tempo change and to continue to change them and re-listen to make sure you have the key or tempo change that you need, before you process and download the file.

Lastly, after processing, the online tool allows you to select from among many different file formats.

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2. Twisted Wave

This Twisted wave system is more complex process. One of the nice features is that in addition to uploading files, you can use a URL to Google Drive or SoundCloud. While the sound quality is good - thought not quite as good as Song Surgeon, it's biggest drawback is that it will process only a mono channel. You need to have a paid subscription to have stereo channel support.

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3. Conversion-Tool

One of the nice things about is the simplicity of the site. You upload your file and then choose from drop down boxes to alter your audio file. Though it offers two algorithms, both algorithms fail to process the test file without introducing some about of distortion as key and/or tempo were changed. Lastly, there are sponsored ads on the site, that can be a distraction.

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4. Audio Speed Changer

One of the strengths of the Audio Speed Changer site supports a wide range of input file formats. On the flip side, the number of output file formats is limited to two: Mp3 and M4a.

It provides what it calls a time-based and a frequency based method, but neither of these provide a clean, non-distortion file after processing. The test file, when processed using this tool, exhibits a distortion in the form of a wobble or tremor, that is not heard in the original file.

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5. Audio Trimmer

The Audio Trimmer site can only change the speed or tempo of an audio file. It Does Not change the key. This makes in much less useful that the others services that do both. In addition, like most other sites, when processing the test file it also introduced audio artifacts in the form of a wobble or tremor, making it less desirable. Lastly, there are a lot sponsored ads on the site, that can be a distraction.

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6. True Tone

The True Tone site is one of the easiest and most intuitive sites that we reviewed. One thing we really liked is that it has a typical audio player look and toggles to change key or tempo. Like other sites, it struggles to process our test file cleanly and introduced some distortion. It addition, perhaps its biggest drawback is that it only allows you to play the file on the site. It does not allow you to process these changes and create a new file that you can download and use, out site of the site.

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7. Onine Tone Generator

The Tone Generator site has separate function for key change and tempo change. This is inconvenient because it means that you have to upload a file twice, and process it twice, if you need to change key and tempo in the same file. The conversion process is slow, the audio quality is average, and when we tested this site there were times when the processed file failed to download.

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8. Voice Changer

We attempted to use this site on two different occasions. It appeared to allow us to upload the file, but after that we could not get it to process the file. It is ranked here in last place primarily because the site is not working. If it were to be fixed, we could listen to sound quality of the processed file and evaluate against the other online services. However, at the time of our review the site was non-functional and therefore it lands at the bottom our our reviewed sites.

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