I am trying to learn how to play blues harmonica better. I have made MP3 files from several of the instructional CDs I have purchased. What I would like to do is playback these files at a slower speed (tempo) without changing the pitch. Then I can play along until I learn the piece well enough to speed things up.

I use my RioCar as a music source on my home network with Hijack allowing me to listen to what I want on a PC. Is there player software that allows slowed down playback from a streamed MP3 file?

I also use a NEXII portable player to listen to these same instructional selections. I need software that would allow me play the original MP3 file at a slower speed and encode a new slow speed version MP3 file. I would then load it on the portable player. I am hoping for feedback from people who have done this and tried various software solutions.

Now that you know what I want to do please feel free to suggest alternatives. I am sure there are more imaginative, perhaps simpler ways to do this.

Michael

I'm sure there are WinAmp plugins that can do this sort of thing, I don't know where they are though. I know you can also do this in many audio-editing packages such as CoolEdit.

If you want to go ultra-cheap, you can use the Windows Sound recorder applet to decrease the speed of a wave file by half. This will make it play more slowly, albeit at a one-octave drop in pitch. This is actually fine for learning how to play a musical phrase, I've done it quite often. You just have to keep in mind that your half-speed instructional version is also one octave lower.

This is essentially the digital equivalent as the "half speed tape recorders" you see for sale in music stores. These things have been around for many decades, just for the purpose of musical instruction, so you'll be part of a grand tradition.

How to: First, get the original WAV file instead of the MP3. For instance, by re-ripping just the WAV from the original CD. Or, if you only have it in MP3 form, use the WinAmp disk-writer plugin to make the MP3 into a WAV. Then open the WAV into Sound Recorder. Then say "Effects/Decrease Speed". Then save it. Bingo, half-speed audio clip.

Tony,

Thanks for your reply and suggestions. A music friend has suggested Transcribe!. It does lots more than allow slowing down the tempo without changing the pitch but it remains easy to use. Best of all it works with lots of sound file formats including MP3. It is shareware, available in Windows and MAC versions, and costs $40. I found the Transcribe! link to similar types of programs (The Competition) useful.

Thanks again for your help.

Michael

/me scrambles to download this nifty-looking "Transcribe" program. COOOOL...

You've probably already found a program that does what you want better, but Acid also does this.


*edit*
Oh, wait, I think you need to make them into WAV's before Acid can do it

How does that work? How can you slow down something without affecting pitch? Just wondering..

Calvin

How can you slow down something without affecting pitch?

With some tricky audio coding. Same way you can change the pitch without changing the speed. It's all DSP-type stuff. You'd be surprised what you can pull off with a little clever mathematics and an audio signal.

You can only go so far before you start to hear artifacts, but for the purpose of just a little bit of pitch correction or speed change, it's practically indistinguishable from the original if the code is good. Many pro audio applications will do this, allowing you to mix two disparate pieces of music together and making them sound as if they were in the same key or the same tempo. Impressive stuff when you see it in action.

Changing an audio clip as much as "Transcribe" does (slowing it to 1/2 or 1/4 speed) introduces audible artifacts, but for the purposes of transcription, it's fine.

Doesn't the SB Live cards from Creative do this as well? I've got a really old original SB Live and you can play about with the EAX filters to make it do pitch changing without affecting the speed. No idea how good it is since it's a bit gimmicky and I only used it once to have a look

- Trevor

My Pioneer DJ-500II cd player was already capable of doing this about 4 years ago when I bought it. Though it has a 10% up/down pitch, the "master tempo" feature (as they call it) is only usuable up to +/- 7%. If it gets pushed more you start to hear it. It's not very obvious, but if you listen closely you'll notice there's something about the music that isn't quit "right".

On a sidenote, the latest product in this series is the DMP-555, which even allow playing (mixing) mp3 cd's! Too cool!

I'm not doubting it can be done. I'm just wondering how?

Calvin

I guess you could do it if you do a FFT on the signal and then just shift everything up in frequency by a predetermined amount and then do an inverse FFT to get your output

- trevor

I do not know how it is done except that, as Tony said, it involves digital signal processing. In my thinking about it I imagine it involves sampling of the original audio, processing to slow down the tempo (stretch out the time scale) and filling in the gaps with a version of the original sampling. In other words if you need to make a quarter note last as long as a half note (slowing the tempo by 1/2) substituting a doubled DSP version of the original note (the equivalent of playing the same note twice as long) ought to do it.

I am certain that the algorithm involved is much more complicated than my imagination. I think I had better stick to trying to play the harmonica! The sample MP3 file on the Transcribe! site is interesting to listen to. It demonstrates the sound quality of slowdown-without-pitch-change. It contains 7 seconds of a guitar solo played quite fast, followed by the same at half speed.

Michael