Change Speed (What is the correct length of a song?)

Some time ago I recorded a couple of now obsolete albums from cassette using Audacity and converted the songs to individual MP3’s. The recordings ended up being a quicker speed than they should be and I intend altering them to correct that using Change Speed.

What I am trying to work out is what is the actual correct length of a song? iTunes and also CD’s quite often seem to list the length of a particular song as being 1 to 3 seconds more than what the old vinyl copies say they are.

iTunes and CD’s include any silence at the beginning and end of songs in their time. Does the vinyl listing of the length of a song include any extra length beyond the actual song itself ?

I don’t know… Sometimes with a fade-out it’s a little fuzzy where the song actually “ends”. And, I don’t know how accurate those published times are.

The best solution might be to find a musician who can help you adjust the speed by the pitch. Once you figure-out the error, I assume all of the recordings have the same error and need the same correction.

Otherwise, since you apparently noticed the problem by-ear so maybe you can adjust by-ear. It won’t be perfect but you should be able to make it better.

It could have been recorded at 44.1kHz been “tagged” for 48kHz playback. The correction would be 44.1/48 (0.919). That’s a very-rare problem but if that correction factor works…

Do you know what went wrong? Maybe it would be best to fix the root problem and re-record? Is it the cassette player? i.e. Did it sound fast when you were recording?

If it sounded OK while recording, tell us about your setup. You might get a sample rate error/difference if you record on one digital device and play back on a different digital device. The 44.1 vs 48kHz issue sometimes happens with an S/PDIF connection.

Thanks for your reply. I was hoping that the vinyl times would be “correct” however as you point out that may not necessarily be the case. I think the cassette player is the problem as it happened on both the albums in question plus another one I recorded (which is available on iTunes).

I am not necessarily looking for a perfect solution. What I am considering doing for one of the albums is comparing the “vinyl time” against the “CD time” and try to guess what I should make the length of each song from there. The other album was not issued as a CD so - as I like to leave around 0.5 second of silence before a song begins and around 3 seconds after it finishes - I am considering adding 3 seconds to the “vinyl time” and see how that works.

If you (or anyone else) have any further tips, I am happy to hear them (keeping in mind I am looking for a reasonably simple solution).

You can do the Limited Variable Scientific Experiment. Accurately time a recording, say 3 minutes, by your watch. You don’t have to actually roll tape. Just use the same setup as you did for the music. Time the resulting sound file and the difference between reality and the file is the Effect > Change Speed correction.

If there is no difference, then your tape machine mechanics are fried.

There is a product note about this. You are probably not going to leave the tape machine to your grandchildren, right? After the last tape, it’s going in the bin. Sometimes these machines go into the bin a little too early.


I will do what you suggest. It is not a top quality tape machine and I am guessing the mechanics are fried. If that is the case, as you say, it could be going in the bin.