Please use the Support forum to ask for help in using MuseScore, not the issue tracker, which is for tracking actual confirmed bugs only. When you post your question to the forum, Include as much information as you can about the problem you are having - what OS you are on (I would guess some version of Windows), where you got lame_enc.dll from, where you installed it, what exactly you are doing that causes the error, the exact text of the error.
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Please use the Support forum to ask for help in using MuseScore, not the issue tracker, which is for tracking actual confirmed bugs only. When you post your question to the forum, Include as much information as you can about the problem you are having - what OS you are on (I would guess some version of Windows), where you got lame_enc.dll from, where you installed it, what exactly you are doing that causes the error, the exact text of the error.