playback is warbled from cassette

I’m converting a cassette to digital, using Windows 10 PC, with a USB port connected from cassette player to computer tower. The first playback sounded fine, but it had another recording mixed with it by mistake. So that got deleted. Next recording was warbled on playback on audacity as well as in the music file. I think the playback speed got changed by accident. What is the normal speed for playback? All the setting are the default audacity settings. What can I do to make the playback clear? I’ve been working on this all day, quite frustrated. And this is a paid job I’m doing for someone else. Time is money. Need to move forward with the project quickly. Thanks

Warbling playback from a cassette is often caused by the cassette tape sticking, which may be due to the cassette being old and used for a long time (the tape tends to become sticky), or the tape being wound too tightly. Old tapes also tend to become brittle and can break easily, so must be handled with care (avoid fast winding to the end - the shock when it reaches the end can snap old tape). Carefully winding the tape through from end to end before playing may help to improve smooth playback.

It can also be caused by the tape slipping between the capstan and the pinch roller. This becomes more likely as these parts of the player gather dust.
Pinch rollers may be cleaned with a little alcohol on a cotton swab stick (Q-Tip). Avoid getting alcohol on any tapes as it will permanently damage or destroy them. Special “capstan cleaning fluid” is also available.

Warbling playback may also be due to the cassette tape being stretched. Unfortunately this cannot be repaired. If the problem happens with just one cassette (others play correctly), and the problem persists after winding the the tape from end to end and back again, then the tape is probably stretched.

See this page in the Audacity Wiki:


To digitally-fix warbling you’ll need other $oftware (and deep pockets).