Chord Pitcher is a Max for Live audio effect that can re-pitch a sound to 4 different ratios in real time, to up to four octaves up or down. This can be great to use with any monophonic instrument, synth
I've written about a few chord plug-ins before. Xeno - Chord Explorer, a Max for Live MIDI effect, strikes me as the most musical I've encountered so far. It offers the 7 diatonic scales, has quite an extensive set of features and all that while it's free.
“Chord Machine” comes in a variety of two Max for Live devices. The original one is a chord sequencer with 4 different parameters made for the Monome 256. "Chord Machine Midi" is a MIDI effect version for everyone who doesn't have this type of controller.
Fabrizio Poce is well known under his moniker J74 in the Max for Live scene and I've written about some of his devices before. While most do cost a little, they're really fantastic (check them out) and must have taken quite some time to build. He recently released the "J74 HarmoTools", a bunch of chord and scale analysing and harmonising devices. All for free.
Ho ho ho and a merry Christmas to all of you! While others might give you a Live Pack based on bells, I'll give you the "Tuned Boing Drum" Live Pack (I've already done bells in May). It's quite the merry sound though.
This tutorial about Ableton Push looks at the Scales settings. You'll get a little crash course in music theory and harmonics as well as learn how to make use of it in compositions.
Practically everything has music hidden inside. Don't believe me? How about the sound of a file right out of the toolbox? The one I used is bendable and makes a cool bouncy boing sound which I closely microphoned and created 3 Instrument Racks with. All are fully macro-mapped and the "File under File" Live Pack works in Live 8 and 9.
You don't know any music theory, but would love to compose more harmonic chords in Live? If you have Max for Live, you could use the Schwarzonator or Nordmann's "Chord Generator".
A while ago I posted the first tutorial video by Ableton on how to use Push. Now there's a second one. This one explains how to play notes or chords and how to use pressure and pitchbend to modulate sound with Push. The arrangement of the notes in patterns is interesting and should make playing easy enough for beginners.