ffmpeg \
-i all_music_clean.m4a \
-i tts/start_end/walk_5_minutes_cool_down.wav \
-i tts/run/run_1_minute.wav \
-i tts/walk/walk_90_seconds.wav \
-filter_complex "\
[0:a]afade=t=out:st=0.0:d=0.5:silence=0.0[bg0_1]; \
[1:a]adelay=2000|2000[fx0]; \
[0:a]afade=t=in:st=8.0:d=0.5[bg0_2]; \
[bg0_2]afade=t=out:st=300.0:d=0.5[bg1_1]; \
[2:a]adelay=302000|302000[fx1]; \
[0:a]afade=t=in:st=308.0:d=0.5[bg1_2]; \
[bg0_1][fx0][bg1_1][fx1][bg1_2]amix=inputs=5:duration=longest:dropout_transition=0[mix]" \
-map "[mix]" -c:a libmp3lame output.mp3