Rodan
Rodan is one of the notable extensions of the slendric temperament, which divides 3/2 into three equal intervals representing 8/7 (tempering out the gamelisma, 1029/1024), reaching the full 7-limit such that 17 of these generators stack to reach the interval class of the 5th harmonic (5/4). It tempers out 245/243, making it a sensamagic temperament, so that 5/3 is divided into two intervals of 9/7; and it tempers out 5120/5103, making it also a hemifamity temperament, so that 9/8 stacks thrice into 10/7.
Unlike mothra, which flattens the fifth to a meantone fifth, the fifth of rodan is slightly sharp of just, ranging from that of 41edo to that of 46edo (with 87edo being an essentially optimal tuning). As a result, the diatonic minor second is compressed, and the interval known as the quark, which represents 49/48, 64/63, and in rodan also 81/80, is even smaller than it is in tunings of slendric with a nearly just fifth. This entails that the MOS scales of rodan cluster even more strongly around 5edo, although this can be thought of as an advantage in that it simplifies the conceptualization of rodan's inventory of intervals; rather than directly using MOS scales, which are either extremely imbalanced or overly large, an approach to rodan may involve picking and choosing which intervals from each pentatonic category to keep in the scale.
As for further extensions, slendric temperaments often find 55/32 at 4 generator steps (tempering out 385/384 and 441/440), giving new interpretations to the quark as 55/54 and 56/55; 55/32 is particularly accurate in the tuning subrange appropriate for rodan, and so harmonic 11 can easily be found at -13 generator steps. The diatonic minor third (32/27) in hemifamity temperaments represents the square root of 7/5, for which 13/11 is a good interpretation (tempering out 352/351 and 847/845), which turns out to place harmonic 13 at -22 generator steps. Finally, 17/13 is a good interpretation of the slendric subfourth comprising two generators, otherwise equated to 21/16 (tempering out 273/272 and 833/832), and this places harmonic 17 at -20 generator steps. Thus proceeds the canonical extension of rodan out to the 17-limit.
See Gamelismic clan #Rodan for more information.
Interval chain
In the following table, odd harmonics and subharmonics 1–21 are in bold.
| # | Cents* | Approximate ratios | |
|---|---|---|---|
| 13-limit | 17-limit extension | ||
| 0 | 0.000 | 1/1 | |
| 1 | 234.482 | 8/7 | |
| 2 | 468.964 | 21/16 | 17/13 |
| 3 | 703.446 | 3/2 | |
| 4 | 937.929 | 12/7 | |
| 5 | 1172.411 | 63/32, 160/81 | |
| 6 | 206.893 | 9/8 | |
| 7 | 441.375 | 9/7 | 22/17 |
| 8 | 675.857 | 40/27 | |
| 9 | 910.339 | 22/13, 27/16, 33/28 | |
| 10 | 1144.821 | 27/14, 35/18, 64/33 | 33/17 |
| 11 | 179.304 | 10/9 | |
| 12 | 413.786 | 14/11, 33/26, 80/63 | |
| 13 | 648.268 | 16/11 | |
| 14 | 882.750 | 5/3 | |
| 15 | 1117.232 | 21/11, 40/21 | |
| 16 | 151.714 | 12/11 | |
| 17 | 386.196 | 5/4 | |
| 18 | 620.679 | 10/7 | |
| 19 | 855.161 | 18/11, 64/39 | 28/17 |
| 20 | 1089.643 | 15/8 | 32/17 |
| 21 | 124.125 | 14/13, 15/14 | |
| 22 | 358.607 | 16/13, 27/22 | 21/17 |
| 23 | 593.088 | 45/32 | 24/17 |
| 24 | 827.570 | 21/13 | |
| 25 | 1062.052 | 24/13 | |
* In 13-limit POTE tuning
Notation
A notation for rodan is listed in the notation guide for rank-2 pergens under pergen #8, (P8, P5/3). The generator is an upmajor 2nd. The enharmonic unison is a trudminor 2nd. Thus three ups equals a diatonic semitone, and three generators equals a perfect 5th. In rodan in particular, ^1 equals ~81/80 and ~64/63, and ^^1 equals ~33/32 and ~1053/1024.
| Ratio | Nominal | Example |
|---|---|---|
| 3/2 | Perfect fifth | C−G |
| 5/4 | Downmajor third | C−vE |
| 7/4 | Downminor seventh | C−vB♭ |
| 11/8 | Dup fourth | C−^^F |
| 13/8 | Dupminor sixth | C−^^A♭ |
Rodan's notation has much in common with that for 41edo and 46edo, since both edos map a minor 2nd to three edosteps. It also resembles the notation for cassandra. All four notations notate the slendric tetrad (1–8/7–21/16–3/2) on C as C–^D–vF–G, and all four notations notate 5/4, 7/4, 11/8, and 13/8 as in the table above. But the notations diverge for other intervals, such as 11/10.
Chords
Scales
Tunings
Tuning spectrum
| Edo generator |
Eigenmonzo (unchanged-interval) |
Generator (¢) | Comments |
|---|---|---|---|
| 7/4 | 231.174 | ||
| 17/13 | 232.214 | ||
| 7/6 | 232.282 | ||
| 21\36 | 233.333 | 36cfg val, lower bound of 7- and 9-odd-limit diamond monotone | |
| 9/7 | 233.583 | ||
| 3/2 | 233.985 | ||
| 24\41 | 234.146 | Lower bound of 11- to 17-odd-limit diamond monotone | |
| 15/14 | 234.259 | ||
| 7/5 | 234.305 | 7- and 9-odd-limit minimax | |
| 11/9 | 234.347 | 11-odd-limit minimax | |
| 75\128 | 234.375 | 128g val | |
| 13/9 | 234.407 | 13- and 15-odd-limit minimax | |
| 15/8 | 234.413 | ||
| 11/6 | 234.415 | ||
| 15/11 | 234.453 | ||
| 13/12 | 234.457 | ||
| 15/13 | 234.470 | ||
| 51\87 | 234.483 | ||
| 5/4 | 234.489 | 5-odd-limit minimax | |
| 11/10 | 234.500 | ||
| 13/10 | 234.507 | ||
| 11/8 | 234.514 | ||
| 13/8 | 234.521 | ||
| 13/11 | 234.532 | ||
| 17/9 | 234.575 | 17-odd-limit minimax | |
| 17/15 | 234.583 | ||
| 78\133 | 234.586 | ||
| 5/3 | 234.597 | ||
| 17/10 | 234.631 | ||
| 17/12 | 234.652 | ||
| 17/16 | 234.752 | ||
| 9/5 | 234.764 | ||
| 27\46 | 234.783 | Upper bound of 11- to 17-odd-limit diamond monotone | |
| 11/7 | 234.792 | ||
| 3\5 | 240.000 | 5f val, upper bound of 7- and 9-odd-limit diamond monotone |
Music
- Pianodactyl (archived 2010) – SoundCloud | detail | play – rodan[26] in 87edo tuning