The builds posted earlier weren't "mp3-free" versions, but here's one that is...
www.un4seen.com/stuff/bass-mf.zipThis update also adds the following BASS_ChannelGetTags option...
#define BASS_TAG_WAVEFORMAT 14 // Audio format : WAVEFORMATEX structure
That can be used to check the format, ie. from the wFormatTag member... 0x1610 = AAC, 0x0161 = WMA, 0x0162 = WMA pro, 0x0163 = WMA lossless.