In 2005, jazz guitarist Gustavo Assis-Brasil released Hybrid Picking For Guitar (review) - a fantastic instructional book covering the technique and implementation of hybrid-picking. Now Assis-Brasil has released a new book entitled Hybrid Picking Exercises - Single Note Permutations. As Assis-Brasil notes in the foreword, if you already own Hybrid Picking For Guitar, this new book can be viewed as supplemental material, though it certainly stands on it's own as well. Whereas Hybrid Picking For Guitar was loaded with eighth note and triplet lines designed to help develop your hybrid-picking technique, Hybrid Picking Exercises - Single Note Permutations, as the title suggests, is strictly an exercise book. It's practice patterns are based on simple 4-note finger shapes, as opposed to actual lines. Assis-Brasil did include some pure hybrid-picking exercises in the previous book, but he takes the idea a giant step further here.
The book is broken down into two sections; Short Exercises and Extended Exercises. The Short Exercises section contains 32 separate exercise patterns for each possible permutation of the 4 fret hand fingers (1-2-3-4, 2-1-3-4, etc). Each exercise spans two to four strings (often skipping a string or two in the process), and includes a combination of picked notes, plucked notes, and hammer-ons or pull-offs. The Extended Exercises section takes those same patterns and moves them up, down, and across the fretboard. At 178 pages, it's a massive amount of practice material, entirely geared towards developing finger independence for both hands.
The whole idea of this book is to get your fingers moving in ways they have not moved before, and it does this quite well. As a guitarist I can tell you, when you make up your own practice patterns, there is a natural yet unconscious tendency to use fingerings and shapes that you already have a good grasp of. Breaking out of that routine can be tough. On one hand, extrapolating on patterns you already play well is a great idea; you'll get more mileage out of a given lick. However, unless you spend a certain amount of practice time on patterns that are outside your comfort zone - patterns that feel downright awkward when you first approach them - you'll be slow to develop good finger independence. For this reason, I enjoy discovering patterns that are totally different from what I normally play or practice. If new, awkward-feeling patterns are what you're looking for also, you'll find plenty of them in Single Note Permutations.
To me, the hybrid-picking style falls under the larger category of "Legato." Better finger independence is something any guitarist can benefit from, but it's an absolute must if you are an aspiring legato-style player. The legato approach (as exemplified by players such as Assis-Brasil, or Allan Holdsworth, or Brett Garsed) lends itself to more free-form sounding lines. Granted, they may not actually be free-form, but if you have the kind of finger independence that the great legato stylists have, you can make it seem that way by relying less on stacked, symmetrical patterns, and more on your own spur-of-the-moment inspiration. Having said that, playing some of the Single Note Permutations exercises with strict alternate picking yielded a great workout for me as well.
Some educators argue that all of your technique should be learned from practicing real music (transcribed lines, etc), and that generic finger exercises will do you a disservice. A valid point, certainly. However, there is still plenty of musical benefit to be had from Single Note Permutations, even though it's exercises are not based on real scales. I found that by taking these exercise patterns and plugging them into actual scale shapes, all sorts of cool lines can be generated. Plus, I'm sure I was able to get the lines down quicker this way (as opposed to starting with the line first), since the contours of the pattern I intended to use were already committed to my muscle-memory before I tackled the line.
Most guitarists have practiced the age-old four-note-per-string left hand permutations to develop finger independence at one point or another (1-2-3-4, 4-1-2-3, blah-blah-blah-blah, etc). By taking those same patterns, and spreading them across multiple strings with hybrid-picking, the exercises in Single Note Permutations will give you a much better workout than the standard four-note-per-string patterns can. Plus, how much musical benefit can you really extract from those old exercises? The permutations in this book easily translate into real lines, which makes it a source of both technical exercise, and musical inspiration.