https://ais.absoluteradio.co.uk/absoluteradio.aac
The latest bass_aac.dll is now 2.4.5.22, dated 2021-06-30, and is now at http://www.un4seen.com/stuff/bass_aac.zip
MusicBee defaults to using the Windows 7/10 AAC codec when playing AAC/M4A; as has been stated by many others before, those with problems using that solution (esp. with Windows 10) can download the bass_aac.dll from www.un4seen.com, drop that into the MB folder and restart. MusicBee will then default to that plugin for AAC/M4A.
Just wanted to note here that the latest bass_aac.dll version is not necessarily in the "bass_aac24.zip" package from the link at the normal un4seen web site (http://www.un4seen.com/download.php?z/2/bass_aac24), but may reside at http://www.un4seen.com/stuff/bass_aac.zip, until the last "in development" version is moved to the "regular" address.
The BASS developer has stated that plugin versions available at the www.un4seen.com/stuff/* address ".. are 'in development' updates that are made available between releases. They are still "release" builds and usually fine for production use."
The latest bass_aac.dll is now 2.4.5.22, dated 2021-06-30, and is now at http://www.un4seen.com/stuff/bass_aac.zip
(modified 2021/07/21)