An actual, true analogy that may shed some light on this subject.

In 1984, Apple released the Macintosh, the first mass-market computer with a graphical user interface (its predecessor, the LISA, didn’t qualify as mass-market due to its outrageously inflated price). It came with a selection of fonts (all named after cities), which could be artificially bolded, italicized, outlined, shadowed, or any combination of the above. These fonts were all bitmapped fonts, and were available in only a few point sizes (9, 10, 12, 14, 18, and 24, for most of the fonts — Chicago only had a 12-point version as I recall, being the main system font used for menus and the like). Still, though, this was far and away better than other personal computers of the time, which could only display the fonts that were built into a text-only monitor, and only print the ones built into the printer.

Adobe changed all that with PostScript and the original Apple LaserWriter. PostScript is an actual programming language (you could conceivably write, say, a text fantasy adventure game in it, or an accounting system, etc., though it is of course optimized for the production of rasterized printed-page images), and supported a new type of font: the outline font. (Prior to this there were vector fonts, designed for pen plotters, that could be scaled, but were made of straight lines only [some could also do arcs, as I recall].) Based on cubic spline mathematics, PostScript font outlines could be of any smoothly-curved shape, as well as having straight lines and sharp corners where needed. The splines could be scaled to any size needed, then rasterized (converted to pixels) with great accuracy. Unlike bitmapped fonts, the PostScript ones could easily have true boldfaced and italicized variations (each actually being a different font, not just the same font made thicker or slanted at an angle as was done with the Mac bitmapped “city” fonts).

Aldus made the first page layout program, PageMaker, which ran on the Mac and used Adobe PostScript fonts and the LaserWriter printer, and the Desktop Publishing industry was born.

Adobe wanted to make money designing high quality outline fonts for PostScript, but there was a legal problem: fonts could not be copyrighted. They were based on the well-known shapes of the alphabet, which had been around since the days of the Romans, with a substantial fraction of our upper-case alphabet (and, indeed, the very word “alphabet” itself!) dating even further back, to the Greeks. So, the legal opinions were that shapes that were simply variations on the alphabet, which is what fonts and typefaces were, could not be copyrighted.

To try to build a viable business model, Adobe heavily encrypted their Type 1 font format with a then-proprietary and non-published algorithm protected by Trade Secret law. They could thus charge high prices for their fonts. And, in turn, while the PostScript language itself was easily duplicated, the encryption algorithm was not, so most PostScript clones of the time could not handle encrypted Type 1 fonts. Adobe even went so far as to cripple a very useful keyword of the PostScript language itself (pathforall), which prevented it from working with paths derived from characters, so that a clever PostScript programmer could not them spit out the actual spline curve coordinates used to make the fonts. This made it much more difficult and time-consuming to do viable effects that a font-enabled pathforall would have enabled, such as writing tiny text around the outlines of large letters.

Adobe had some competitors in the outline font market, each with their own font systems, but none were as popular as Adobe. Bitstream was easily #2 at the time.

Adobe also charged heavily for rights to their PostScript interpreter, needed for the Apple LaserWriter, and also for the subset needed to display Type 1 fonts (i. e. Adobe Type Manager) in Mac OS and Microsoft Windows. Because of this, both Apple and MS had to pay hefty royalties to Adobe, and they were getting sick of it. So, the two companies, in one of the few times they joined together against a common foe, came up with TrueType, a simpler outline font algorithm (based on quadratic splines, which can be calculated faster but are not as versatile as cubic splines, and generally require more data to produce a similar shape) that could be incorporated into the OSes themselves.

Adobe was incensed. Since TrueType was going to be an open standard, they could see the writing on the wall as long as PostScript and the Type 1 format remained closed. But if they opened the format, there would be no legal protection for their Type 1 fonts.

Just as Apple and Microsoft, normally bitter competitors, had banded together against Adobe, so Adobe too worked in cooperation with its rival Bitstream to get the font law changed. In court, Adobe and Bitstream each demonstrated their version of a common font, and noted that they looked almost identical on paper. Then they showed the court the inner workings of both fonts, and how the outlines were constructed, and the two were wildly different internally.

The court ruled, and this has been upheld to this day, that while the shapes of fonts still cannot be copyrighted for the same reason they couldn’t before, the internal code that makes up the fonts can be copyrighted, as software or computer data.

With this method of protecting their fonts, Adobe was able to blunt the impact of TrueType somewhat, and maintain its own presence in the Desktop Publishing field for both Apple/Mac and Microsoft Windows, by opening up the Type 1 font encryption and making the Type 1 font format a publically known format. Now people could make their own Type 1 fonts, but could not legally rip off fonts from Adobe, Bitstream, or other foundries. They could make look-alike fonts, but could not just copy the internal font code and tweak it or whatever, then sell the result as their own work.

With this analogy, Styles are like Fonts. Two Styles could conceivably sound pretty much identical, but have different MIDI code internally, or contain other information that is non-MIDI and proprietary (e. g. the CASM portion of a Yamaha StyleFileFormat style). With the precedent established for fonts, styles could indeed be copyrighted insofar as their internal data goes, even if the sound of the style cannot be because it lacks a melody or sufficient measures to be considered a new and unique musical creation.

With this in mind, Yamaha is well within their rights to protect their styles insofar as the data itself goes. Whether this is wise or foolish of them is another matter (I tend toward the latter). But they cannot keep someone from creating styles of their own that sound just like the Yamaha styles, so long as the person made them from scratch without “taking apart” the Yamaha styles. The two might sound similar, but have substantially different internal data representations, just as the Bitstream and Adobe versions of the same basic font were very drastically different “under the hood.”