JAVASCRIPT IPF FINDER
v1.0b12 ©2006 Michael Norris
Date modified:
26 April, 2008
Based on the writings of Peter Schat and Jenny McLeod
ABOUT
This is a little Javascript program that lets you click on a group of pitch-classes, and then returns a bunch of information about them, including the Intervallic Prime Form (IPF). Much reference is made to Tone Clock theory, drawn from the IPF tables in Jenny McLeod’s “Chromatic Maps”* (based on Peter Schat’s
work). At the bottom of this page is a glossary explaining (some) of the terminology.
One day I'll get round to explaining everything... :-)
Please tick the notes in the chord then click 'Calculate': |
Sample 12-note steering: |
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* Unfortunately Jenny's writings are currently unpublished, though there are possibilities for future publications. Watch this space.
** NB: existing name may only apply to certain voicings or inversions
GLOSSARY
IPF: The Intervallic Prime Form. Like the "Normal Form" in Forte's writing, but a little easier to work with, IMHO. The most 'compact' form of the pitch-classes, where the intervals between notes are shown (1=semitone, 2=whole tone, etc.). Sometimes an alternative IPF is given in brackets.
Existing name: If this set of pitches has an English name it will appear here. I have expanded this section from Chromatic Maps to include chords that are often used in jazz (including so-called "rootless" voicings). If the pitches are a subset of a particular scale, then the scale will appear here parenthesised.
Pitch-Class Set: The PC Prime Form taken from Allan Forte's The Structure of Atonal Music.
Tone Clock Name: The roman tone-clock names, associating the IPFs with the twelve "hours". Not all IPFs have an associated TC name.
Tone Clock 12-note Steerings: Some IPFs can be transposed so that each new set of pitch-classes uniquely combines with the old sets to create the 12 chromatic pitch-classes. For instance, a 3-note chord would be transposed 4 times, while a 4-note chord 3 times. The "base" pitches for these transpositions themselves form a set of interval-classes, which is given here in its tone-clock name.
Other Identities: Any other names for this IPF.
Mode subset: Taken from Messiaen's modes of limited transpositions. If the IPF forms a subset of one of Messiaen's modes, then this is given here.
Chromatic Complement: "Complement" as in set theory. If the notes of the IPF are subtracted from the 12-note chromatic scale, the resulting pitches themselves form an IPF, which appears here.
DOWNLOAD INSTRUCTIONS
This programme can be saved to your hard drive so you can use it without needing to be connected to the Internet. Please follow the instructions below.
1) Choose "Save As…" from the File menu, and save this document as an HTML file
2) You will also need to download the images of the notes & clef from this file: images.sit to your hard drive, and decompress using Stuffit Expander. Make sure you put this folder in the same location as the ipf.html file.
3) To run this programme, simply double-click the downloaded html file.