Re: question about transposing an interval of a 4th

[M Watts]

Tim Reeves wrote:
> > Umm... yeah.  The fact that he thinks this answers the question
> > gives me *less* confidence that he knows what he's talking about.
> > If he wanted it a perfect fourth lower, then \transpose does the
> > job.  And normally when somebody says "a fourth lower", they mean
> > a perfect interval.  If he wants it a variable fourth lower, then
> > it's not doable without scheme.
> >
> > - Graham
>
> Yes, a variable fourth, if you want to call it that - you finally got it.
> This is like the not-so-helpful answer "You can't get there from here."
> It just took about 20 messages to get to that conclusion.

Actually, there is a way, but it's just something to muck around with, 
and takes a lot longer than scrawling stuff by hand on a sheet of ms paper.

Mididings, the python-based midi router from 
http://das.nasophon.de/mididings/, includes a 'diatonic harmonizer', 
which allows you to add or substitute a harmony line at a specified 
interval from the notes being played, with respect to the home key.

So you could:

1) download & install mididings

2) save the following as test.py

# start of file
# harmonizer.py - example usage of the diatonic harmonizer
#

from mididings import *
from mididings.extra import Harmonize

# substitute a fifth above each note played -- equivalent to a fourth 
below, this only works upwards --, based on the D Major scale
run(
   Harmonize('d', 'major', 'fifth')
)
# end of file

3) start Jack

4) run python ./test.py

5) connect a (virtual) midi keyboard to mididings input; connect 
mididings output to a recorder or sequencer app capable of saving a midi 
file

6) run midi2ly on the resulting file
> Merry Christmas!

Ditto.
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