A DJ's Mac holds the music, the analysis files, and often a second copy for USB

For a DJ, the music is the main cost, and lossless libraries are large. DJ software adds analysis data for every track, and preparing USB sticks for club players copies tracks again. It is common to find the same library twice on one Mac.

Where each app keeps its data

du -sh ~/Library/Pioneer 2>/dev/null                           # Rekordbox
du -sh ~/Music/_Serato_ 2>/dev/null                            # Serato, on the Mac drive
du -sh ~/Documents/Native\ Instruments/Traktor* 2>/dev/null    # Traktor

Analysis data is typically small next to the music, but Rekordbox's waveform and cue data for a large collection can reach GB.

The duplicate library

• Music downloaded from a store lands in Downloads, then gets copied into a music folder.
• Exporting to USB for a club player copies every track in the playlists.
• Converting formats, for example AIFF to MP3 for a stick, leaves both.

# Audio files, by size, across common folders
find ~/Music ~/Downloads ~/Desktop -type f \( -iname '*.aif*' -o -iname '*.wav' -o -iname '*.flac' -o -iname '*.mp3' \) -exec du -ch {} + 2>/dev/null | tail -1

A setup that works

• Keep the library in one place, often an external SSD, and point the DJ software at it.
• Treat USB sticks as exports, never as the master copy.
• Clear Downloads after importing new tracks.

Related: duplicate songs, Mac storage for musicians.