Are there any negative sides in using an old version of bass.dll?
Well, you miss out on all the changes, improvements, and fixes that were made since the 2.4.12.x release. Which is why it's a great thing that Steven released the new MusicBee 3.2 patch above that allows the newer versions of bass.dll to be used without any problems in MusicBee (THANKS!). Below is a partial list of the changes made in the newer 2.4.13.x bass.dll, from the un4seen readme file:
2.4.13.8 - 6/2/2018
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* Indication of a file's original sample format being floating-point
BASS_ORIGRES_FLOAT (BASS_CHANNELINFO/SAMPLE flag)
* Some extra sample data is retained to account for device latency in data retrieval
BASS_ChannelGetData
* FFT window is shortened to match amount of available data when less than FFT size
BASS_ChannelGetData
* FFT level adjusted to be approx the same regardless of amount of available data
BASS_ChannelGetData
* Fix for crash when decoding channels are dissociated from a device
BASS_NODEVICE (BASS_ChannelSetDevice option)
2.4.13 - 19/12/2017
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* WASAPI output on Windows (DirectSound is fallback/optional)
BASS_DEVICE_DSOUND (BASS_Init flag)
BASS_CONFIG_DEV_BUFFER/NONSTOP (BASS_SetConfig options)
BASS_CONFIG_SRC/_SAMPLE (BASS_SetConfig options)
BASS_ATTRIB_SRC/NORAMP (BASS_ChannelSetAttribute options)
* Default output device following support extended to Windows Vista and OSX
BASS_CONFIG_DEV_DEFAULT (BASS_SetConfig option)
* Seamless playback buffer length changing
BASS_ATTRIB_BUFFER (BASS_ChannelSetAttribute option)
SYNTH example updated
* Access to the final output mix for applying DSP/FX
STREAMPROC_DEVICE (BASS_StreamCreate option)
BASS_CTYPE_STREAM_DEVICE
FXTEST example updated
* Dissociating of decoding channels from a device
BASS_NODEVICE (BASS_ChannelSetDevice option)
* Volume attribute levels above 1.0 for amplification
BASS_ATTRIB_VOL (BASS_ChannelSetAttribute option)
* Logarithmic attribute slides
BASS_SLIDE_LOG (BASS_ChannelSlideAttribute flag)
* Volume & panning attribute affected level retrieval
BASS_LEVEL_VOLPAN (BASS_ChannelGetLevelEx flag)
* Volume level adjustment effect
BASS_FX_VOLUME (BASS_ChannelSetFX type)
BASS_FX_VOLUME_PARAM structure
* Asynchronous pre-buffering
BASS_CONFIG_NET_PREBUF_WAIT (BASS_SetConfig option)
BASS_StreamCreateURL/FileUser
CONTEST and NETRADIO examples updated
* Decoding channels can be dissociated from a device
BASS_ChannelSetDevice
* Resetting of user file streams/decoders
BASS_POS_RESET (BASS_ChannelSetPosition flag)
* Relative seeking
BASS_POS_RELATIVE (BASS_ChannelSetPosition flag)
* RIFF cue points chunk retrieval
BASS_TAG_RIFF_CUE (BASS_ChannelGetTags type)
TAG_CUE structure
* RIFF sample chunk retrieval
BASS_TAG_RIFF_SMPL (BASS_ChannelGetTags type)
TAG_SMPL structure
* Support for Category/Description/Grouping/Keywords/Lyrics MP4 tags
BASS_TAG_MP4 (BASS_ChannelGetTags type)
* Separate channel type for dummy streams
BASS_CTYPE_STREAM_DUMMY
* Stalled internet stream buffering progress retrieval
BASS_FILEPOS_BUFFERING (BASS_StreamGetFilePosition mode)
CONTEST and NETRADIO examples updated
* Playlist recursion depth config option
BASS_CONFIG_NET_PLAYLIST_DEPTH (BASS_SetConfig options)
* Push file system read functions can now return 0 without ending the file
STREAMFILE_BUFFERPUSH (BASS_StreamCreateFileUser system)
FILEREADPROC
* 16 point SRC is used by default when SSE is available
BASS_CONFIG_SRC (BASS_SetConfig option)
* Mono downmixing for all file formats in sample loading
BASS_SAMPLE_MONO (BASS_SampleLoad flag)
* Mono OGG stream downmixing
BASS_SAMPLE_MONO (BASS_StreamCreateFile/User/URL flag)
* Media Foundation availability detection
BASS_CONFIG_MF_DISABLE (BASS_GetConfig option)
PLUGINS example updated
* AudioTrack output on Android
BASS_DEVICE_AUDIOTRACK (BASS_Init flag)
* Support for Android Media codecs
BASS_StreamCreateFile/User/URL
BASS_TAG_AM_MIME/NAME (BASS_ChannelGetTags type)
BASS_CONFIG_AM_DISABLE (BASS_SetConfig option)
* Panning fix for MOD files created with ScreamTracker 3
BASS_MusicLoad
* Fix for compressor and distotion DX8 effects with floating-point data on Windows
BASS_FX_DX8_COMPRESSOR/DISTORTION (BASS_ChannelSetFX types)
* Fix for plugin freeing issue on 64-bit platforms (HPLUGIN is not library address any more)
BASS_PluginLoad
BASS_PluginFree