91 Rock: Guitar Song Generator

91 Rock writes complete rock songs and plays them with a band. Press write and
you get a whole arrangement — intro, verses, pre-choruses, choruses, a bridge
and an outro — played by two double-tracked rhythm guitars, a lead guitar, a
clean guitar, bass, keys and a drum kit, each through its own amp.

The guitars and drums are real recordings. The electric guitar is an Epiphone
recorded direct, sampled up the neck at three dynamics, and the kit is a vintage
drum kit recorded close and overhead, with several velocity layers and takes of
nearly every hit. The bass is a four-operator FM engine. All of it ships inside
the app, so it works with no network at all.

The songs come from chaos maths. A Lorenz attractor draws the melodic line and
a logistic map shades the drums, so no two bars need be alike. Chaos on its own
is noise, so a small model filters it: it is rewarded for consonant intervals and
learns as it writes. The CHAOS / TASTE slider decides how much say each one gets.

Thirteen styles, and each one is a whole band: its riffs, its drummer, its tempo
range and its amps. Grunge, Metal, Heavy Metal, Death Metal, Groove Metal, Rap
Metal, Progressive, Rock Ballad, British Rock, Country Rock, Alternative, Punk and
Stoner / Sludge. Tick STYLE LOADS RIG and each style brings its own amps and
drive pedals with it.

The rig is the other half of the sound. Four amp channels — bass, rhythm, clean
and lead — with twelve voicings from jangle to siege, three cabinets, gain and a
four-band tone stack on each. Nine one-click rigs, from Seattle to Basement. A
pedalboard with wah, two overdrives, a phaser, chorus, tremolo and a spring
reverb. A plate, a drum room and a tape delay on the desk.

Every song is built from its seed. Write the seed down and you can have that
exact song again, note for note. A seed from the browser version rebuilds the
same song here.

You can play over it, too. The pads are the notes of the song's key rather than
a piano keyboard, so nothing you touch is wrong, and the sixteen-step lane runs
in time with the song and follows your host — with palm mute for the guitars.
Both play any part you like through that part's rig and out on its MIDI channel.

Turn on RADIO and it keeps playing, picking a new style, key, scale and tempo for
every song.

You also get:

• 13 styles, 14 scales, 12 keys, tempo and density
• 12 amp voicings, 3 cabinets, 9 rigs and a seven-pedal board
• 9 keyboard voices, from organ and Mellotron to clavinet and drone
• Sampled or synthesised drum kit, switchable
• Six-part mixer with a meter on every part
• MIDI in, so your keyboard plays whichever part you have selected
• Export a MIDI file, a WAV mix, or stems — one WAV per part (in the app; in a
host you record the audio there)
• A note and a MIDI channel for every drum, not one channel for the whole kit
• UI scale, so the panel is not tiny on a big iPad
• Live spectrum and waveform, and the chaos engine drawn as it runs

Two Audio Units, an instrument and a MIDI processor. Each part sends on its own
MIDI channel and every drum has a note and a channel of its own, so one instance
can drive a rack of them. The MIDI version passes your keyboard through instead
of swallowing it. Both follow your host's tempo and transport, and one install
registers both.

The app is free and nothing in it is held back. Using the Audio Units inside
other apps is a one-time purchase, and each AUv3 session plays for two minutes
first so you can try them properly.

No account, no ads, no subscription. Works offline.

Samples: Karoryfer Emilyguitar and Big Rusty Drums, and two voices from the
Versilian Community Sample Library, all CC0. Typefaces: JetBrains Mono and Roboto
Condensed, SIL Open Font License 1.1.