Authoring Lower Difficulties

(Please note that this is an unfinished draft from my notes. I'm posting it as-is because I'm unlikely to finish it any time soon, and unfinished online is better than not online at all. There's no images, and while I tried to finish it with some pointers from memory and studying my old charts for what I did, I likely forgot a bunch of edge cases. This is a good starting point, nothing more.)

Lower difficulties on guitar and bass tend to either confuse or bore charters, and for good reason. They're intentional undercharts, boring to play, boring to chart. Right?

Wrong. Lower difficulties are not only necessary for a good, game-quality chart, but GH2 will crash on lower difficulty chart load without at least some notes on those lower tracks. I have friends who are curious about GH, but are by no means Expert players. No lower difficulties mean they can't play, and that's not fair.

So where do you begin with reductions? Here's some good starting points.

The gist of lower difficulties

The best way to look at authoring lower difficulties is by imagining the riff played by novice real guitar players. Think about the details that they'd leave out, depending on their skill level:

They'd likely play simpler versions of chords in the riff.
They'd keep things on downbeats, half notes and quarter notes, because it feels more rhythmically solid.
Flourishes and details, like muted strums or bends, probably get left out.
They need more time to shift their hand positions, so fast shifts up and down the neck get replaced with pauses. Sustained notes are likely to get cut off earlier.

A good example would be how three different novice players might play Nirvana's "Smells Like Teen Spirit":

A pure beginner might play only the power chords without any of the mutes or upstrums.
A slightly better player might add some mutes, but keep the riff to downstrokes.
A decently capable amateur might play the right rhythm, but play more basic power chords as opposed to the extra intervals in Kurt's chords.

You'll want to replicate this feeling for your lower difficulties. Hard is an easier Expert with fewer flourishes and without three note chords, Medium is the skeleton of the guitar part, recognizable as the real rhythm but without any frills and only over four buttons, and Easy is a chordless three button version of the most basic rhythm of the part.

One final note: it's good to simplify sequentially. Chart your Expert part, then copy down to Hard, simplify, copy down to Medium, simplify, then copy down to Easy and simplify. Obviously, anything not played on a higher difficulty will not be played on a lower difficulty.

Simplifying for Hard

Always remove:

Three note chords: Hard does not have any three note chords. If the three note chord is a variation on a two note chord in the same riff, simply chart that two note chord again for consistency. Otherwise, removing the middle tone of the chord or the least emphasized tone of the chord works just fine.
Quick four fret jumps: You should leave at least a quarter note gap between subsequent Orange and Green notes. This is because Hard players can usually handle four buttons at a time, but have limited ability shifting their hands to cover the fifth note, whether that be Green or Orange at that time.
32nd or faster strumming: This might be dependent on song tempo, but I struggle to think of a slow enough speed that strumming at that subdivision would feel fair to a Hard player. Remove every other note. (In the interest of clean charting, if the strumming is between multiple frets, make sure each fret change falls on a downbeat for comfort.)
Sixteenth or faster note runs: For fast tapping or HO/PO patterns, it's better to identify the pitch extremes and keep those notes and simplify the in-betweens. Simply removing every other note may lead to a more confusing pattern than the Expert chart, like if the guitarist is playing a repeating triplet pattern, Orange-Blue-Yellow. In this case, remove the middle note of each run and simply have player alternate between the Orange and Yellow in a galloping pattern.

Maybe remove:

Minor variations in playing: Lower difficulty players really prefer consistency and getting into a groove. Even if it's not audibly accurate, simplify your parts so they're more repetitive. This is entirely subjective and based on feel, but extra notes over chords, extra strums that aren't repeated, those tend to be a good place to simplify.
Sixteenth pickup gem strumming: If, for a particularly funky song, quick muted strums to ringing chords are essential to the groove of the rhythm of the piece, identify the rhythm, keep the pickup gem, and simply thin out before it and after the chord. Otherwise, it's wise to remove them so Hard players have less to play and an easier time reading the chart.
Continuous eighth note playing: Depending on tempo and complexity of the melody (players can keep up with eighth notes if they're on one color, but maybe not across multiple colors), remove some of the notes in a continuous eighth note pattern. Consecutive eighth notes are certainly okay, but again, depending on tempo, removing one every measure or two or so helps to keep players from getting left behind. For consecutive eighth note chords across multiple colors, groups of three with a quarter note of space feels really good.

Simplifying for Medium

Always remove:

Anything on Orange: No hand shifting on Medium! This means you'll have to readjust your run wrapping and which chords you use. With one fewer button, it makes it that much more likely you'll have to reuse pitches and chords. This is okay! We're not interested in accuracy on the lower difficulties, we're interested in playability.
Sixteenth or faster strumming: Everything should be eighth notes or even slower, depending on tempo. You should be able to downstrum every single note on Medium, as players starting out aren't usually comfortable strumming up (usually, they're just using their thumb to press the strum bar down).
Sixteenth note sustain gaps: Sustains should be pulled back an extra sixteenth, leading to an eighth rest between sustains and notes. If this makes the sustain too short, especially with the slower fretboard speed, remove the sustain entirely and leave it as a single strum.

Maybe remove:

Offbeat strumming: This, again, is based on the rhythm and tempo of the song. You're trying to determine which beats are the strongest on Medium and author those, letting Medium players feel the intended rhythm without any extra frills. If those notes are on offbeats, it's okay to author them, just thin out what's around the offbeats instead. A well-placed eighth note can actually make a section much more interesting to play.

Simplifying for Easy

Always remove:

Anything on Blue or Orange: That means you only have three buttons to work with. Readjusting your run wrapping at this difficulty usually just means implying the upwards and downwards movement over the three buttons. Notes on Easy are far too slow to feel like proper runs, but again, that's okay. It's a good idea to make use of the Green-Red-Green-Yellow (or flipped, Yellow-Red-Yellow-Green) pattern on Easy, if only to have another pattern that isn't simple repeating notes or ascending/descending notes to play.
Chords: There's no chords on Easy. If you have chords that share notes, simply use whichever note isn't shared when you simplify.
Eighth or faster strumming: You won't be able to fit everything on strong quarter notes for most songs, but leave a quarter rest or longer between notes where possible. If it's truly important to the rhythm, you can have a single adjacent eighth note, but no more than that.
Eighth note sustain gaps: There should now be a sixteenth triplet (sextuplet, 24th note, 1/24, whatever you wanna call them) amount of space between the end of a sustain and the next note. Again, if the sustain becomes too short, make it a single strum. The extra readability will be much appreciated by your Easy players.