Apple Loops and your own samples

Besides synthesis and the sample packs, claudius plays three kinds of recordings: Apple Loops when GarageBand or Logic content is installed, cuts of songs you give it, and any audio file a script names.

Apple Loops

Where claudius finds them

GarageBand and Logic keep a database of every installed loop with its tempo, length in beats, key and scale, instrument, genre and mood. claudius reads the newest LoopsDatabaseV*.db in ~/Music/Audio Music Apps/Databases or in GarageBand’s container (~/Library/Containers/com.apple.garageband10/Data/Music/Audio Music Apps/Databases), read-only, and keeps the loops whose files exist. A full install has about 14,000; claudius doctor counts them:

  ok  Apple Loops     14096 loops and samples

The count includes your user library. When there is no database, every Apple Loops feature quietly falls back to synthesis or the packs.

How a song uses them

Drum one-shots. When make, song() in a script, or new_song writes a drum lane, it may cut the lane’s sound from a loop instead of synthesizing it: a kick from a loop whose subtype is Kick, a hat from a Hi-hat loop, a clap from a loop with “Clap” in its name, percussion from Clave, Conga, Bongo or Cowbell loops. Loops tagged with a GarageBand genre that suits the song’s genre (Deep House and Tech House for house, Hip Hop for trap and lofi) are four times as likely. The chance is --samples, or samples in song(); it is 0.75 unless you change it, for make, scripts and new_song alike, so the same seed makes the same song everywhere. When the genre puts the song’s drums on a sample-pack kit, the kit wins.

To cut a hit, claudius finds the onsets in the loop and scores each hit by its level, the room before the next hit, how much of the previous hit bleeds into it, and whether its decay suits the lane (long for a kick, short for a closed hat). The best one is trimmed to its decay, faded, normalised to −1 dBFS and cached as a WAV in ~/Library/Caches/claudius/samples/ (~/.cache/claudius/samples/ on Linux), so the loop is read once. The track’s sound then reads like hat cut from 'Silver Hi-Hat 04' (Apple Loops). Whether a lane uses a one-shot is drawn the same way with or without Apple Loops, so the drum patterns of a seed are the same on every machine and only their sounds differ.

Loops. House, deep house and techno have a percussion loop part called top. claudius picks a Drums or Percussion loop of a suitable subtype and genre within 23 % of the song’s tempo (the closer, the likelier), warps it to the tempo, and plays it in the sections that list top. Tonal loops are also transposed to the song’s key by the shortest way, a minor loop to the minor tonic (the relative minor in a major key).

Loop families. make --loops, song("house", #{ loops: true }) and new_song with "loops": true build the whole song around a family of loops produced together: loops in one folder, at one tempo, whose names share a prefix before the instrument word (“Bliss Abyss” in “Bliss Abyss Chord Layers 01”). The song takes the family’s tempo and key, reads the chords of its harmony loop bar by bar from their pitch content (helped by the family’s bass loop), and plays the family’s chords, bass and beat loops as tracks, the way you would start a song in GarageBand. Families with a bass loop and a genre that suits the song are favoured.

Scripts. .bank("apple") cuts drum names from Apple Loops instead of synthesizing them: s("bd*4, [~ cp]*2").bank("apple").

Warping

A loop plays at the song’s tempo and key through Signalsmith Stretch, which changes tempo and pitch in one pass. When the tempo changes by less than 1.5 % and the key not at all, claudius resamples instead (varispeed), which adds no artefacts at all. The loop is stretched as three copies end to end and the middle one kept, so it wraps without a click. Warped loops are cached in ~/Library/Caches/claudius/stretched/.

The licence

Apple’s licence for GarageBand and Logic content lets you use the loops in music you make; read Apple’s software licence agreement for the exact terms. claudius reads the loops where GarageBand or Logic installed them and never copies them anywhere, except the one-shots it cuts, which stay in its cache. It does not redistribute them, and nothing in the claudius repository or its releases contains Apple content.

--no-library (on make, evolve, studio, serve and mcp) keeps Apple Loops and your user library out of the song while the sample packs still play; --synth-only keeps the packs out too; --samples 0 keeps only the one-shots out.

Chopping a song

claudius chop turns a recording into material:

claudius chop ~/Music/reference.mp3 --bars 2

It analyses the song (tempo, downbeat, key, sections), then writes into out/chops/<file name>/:

• one loop per section, --bars bars long from the section’s first downbeat (01-intro-2bars.wav, 02-drop-...), tagged with the tempo, the length in beats, the key and the section’s energy;
• a kick.wav, clap.wav and hat.wav, each cut from the sparsest section that still has that instrument.

Each file is added to the user library, ~/Library/Caches/claudius/user/library.json, which claudius merges with the Apple Loops index: from then on, the one-shots can be picked for drum lanes like Apple Loops one-shots are.

--find "a vocal chop" also cuts out the moments that best match a description, using earshot’s search, as find-a-vocal-chop-1.wav and so on (--top of them per description).

Flipping a recording into a song

claudius make --sample <file> builds a song around a recording, the way a producer flips a sample:

claudius make --genre lofi --sample out/chops/reference/03-drop-2bars.wav

• The recording’s tempo, length and key come from the user library when it is a chop. Otherwise claudius analyses it with the genre’s tempo range and uses 4, 8, 12 or 16 beats of it.
• It is warped to the song’s tempo and transposed to the song’s key by the shortest way.
• Six times in ten (when it is at least four half-beat slices long), it is re-chopped: an eight-slice motif that starts each half bar on the slice of the same position and fills the rest with random slices. Otherwise it plays as recorded.
• It becomes a loop track named sample1 (then sample2 …), with the role sample, ducked under the kick and sent to the reverb, and plays in the drops, hooks and grooves, and in some breaks.

The song’s history records it as flipped '<file>' (<tempo> BPM, <beats> beats, transposed <semitones>), with , re-chopped at the end when it was.

To write a whole new song on another song’s skeleton instead, use claudius remake; see Remaking a song from audio.

Files in scripts

A script plays any audio file through .s() on a note(), n() or chord() pattern:

track("vox", note("c4 ~ c4 [c4 c4]").s("/Users/me/Samples/vox.wav"));

• The file plays like a sampler: c4 at its recorded pitch, other notes faster or slower.
• On a track whose role is not a drum role, each note stops at its length plus 50 ms; drum roles play the whole file.
• A name counts as a file when it contains / or ends in .wav, .mp3, .aif, .aiff, .flac, .caf or .m4a. It cannot go inside a mini-notation string, where / means “slower”.
• claudius decodes WAV, AIFF, FLAC, MP3, AAC and ALAC (M4A), CAF and Ogg Vorbis itself, and asks ffmpeg for anything else when it is installed.

The song stores the file’s path, not its audio, so moving or deleting the file breaks the song. Every decoded file is cached as raw 48 kHz audio in ~/Library/Caches/claudius/decoded/ (about 23 MB per minute of stereo), keyed by its path, size and modification time.

What a shared claudius may read and write

A claudius only you can reach reads and writes wherever you ask. A claudius others can reach checks every path it is given against a list of folders:

The checks:

• Reading. A file named in .s(), opened with load / open, or given to analyze or remake must exist and, after links and .. are resolved, lie inside one of the folders. Opening a blueprint.json also checks every audio file the song plays.
• Writing. save may create a folder when its nearest existing parent lies inside one of the folders and the rest of the path is plain names, so <allowed>/../escape is refused.

Refusals name the path. A path outside the folders gets the same answer whether or not it exists, so a shared claudius does not tell anyone which files you have; does not exist is said only of a path inside them. The last line comes from a claudius whose sample packs folder was /tmp/claudius-packs-demo (CLAUDIUS_PACKS):

/etc/hosts is outside the folders this claudius may read
/tmp/cl-elsewhere is outside the folders this claudius may write
track 'v': /etc/hosts is outside the folders this claudius may read
track 'v': /tmp/claudius-packs-demo/nope.wav does not exist

A folder that does not exist yet is not on the list: until something creates ~/Music/claudius, a shared claudius refuses to save there (Troubleshooting). Sample-pack instruments and Apple Loops are found by name, not by path, so they play in every mode. The security model explains the policy and its limits.