Only songs that are DRM-free can be converted.
It can produce many kinds of files, including AAC, MP3, and Apple Lossless.
To enable iTunes to create MP3 files:
Launch iTunes.

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On a Windows PC, go toEdit>Preferences.
On a Mac,go toiTunes>Preferences.
On theGeneraltab, selectImport tweaks.

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Select theImport Usingdrop-down arrow and chooseMP3 Encoder.
Select theSettingdrop-down arrow and choose a quality setting.
Choose either theHigher Qualitysetting, which is 192 kbps or chooseCustomand select256 kbps.

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Don’t use anything lower than the currentbit rateof the AAC file being converted.
If you don’t know it, find it in the song’sID3 tags.
To select multiples files, pressCtrlon Windows orCommandon Mac and click each file.

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ITunes notifies you if any of the songs you choose cannot be converted due to DRM restrictions.
Deselect those songs to proceed.
Wait while the files are converted.
Then, go to theFiletab and look in theKindfield.
If you don’t want the ACC files,delete the song filesfrom iTunes.
Most people don’t notice this compression.
This means that AAC and MP3 files are already compressed.
Converting the song to a new format further compresses it.
Ensure the best audio quality for files by converting from a high-quality original, rather than a compressed file.
If you don’t have a CD, find alossless versionof the original song to convert.