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WEBVTT
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hi
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i'm zachary canfer and this is waving
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and repetitive repetitive repetitive
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music over quarantine i've been bored
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and i found this android app that has a
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bunch of mini games
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one of which lets you compose music
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and it works but i
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want a little bit more functionality
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than it offers it's not very flexible
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so i thought what if i made this
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what and what programs could i make this
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in that are really flexible are really
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customizable
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emacs so i looked into it and
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emacs can play sounds right if you hit
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control g a couple times you'll hear
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like an error tone
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and it turns out that that is actually
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playing a wave file
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but what's a wave file
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well it turns out that wave is a musical
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file format
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or really an annoying file format
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so data in it can be an unsigned integer
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or a science integer it's not consistent
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and it's little ending by default which
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is not the way i like to think about it
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now you can set a wav file to be big
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endian but if you do that
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emacs can't play it so little ending it
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is
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there's also duplicate data fields
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here are some fields that are fine but
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then there's a fourth field that's
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calculated based on multiplying two of
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the other ones together
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and then there's another data field
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that's you multiply those three ones
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together so it's just repetitive and
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unnecessary but you have to do it or
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it's not a valid wave file
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also the last part of the file is
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described as data
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or as one website i found said
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the actual sound data now
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i don't know about you but when i see
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that i think
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what is a data it turns out
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that sound is just a wave and
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the data is just a bunch of measurements
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of the height of that wave forming each
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sample
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so this wave starts at 8 goes 9 11 13
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14 15 and then back down and if you just
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take those measurements those numbers
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put them in a file that's all your data
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is
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all right let's go to a demo of my
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program
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so this is what z music looks like the
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blue highlighted row is a single beat
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there's 16 of them in this z music file
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and each dash in the row
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is a single note increasing starting
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really low all the way on the left and
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going up
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as we go to the right so if we started
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playing
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we won't hear anything but we'll see the
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highlighted beat is the currently
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playing one
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and we see that it loops so we can stop
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it
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and now we can click to add some notes
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even more than one note at the same time
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works
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and we can even add notes while it's
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[Applause]
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playing
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[Applause]
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okay here are some other features that i
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didn't have time to demo
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so you can save the music to a file and
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this is interesting because normally
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if there's no note in a beat we just
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don't play that beat
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but if you're writing to a file you have
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to put something in
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so when it's playing it knows to not
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make a sound there
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we can also use different scales we're
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using the minor pentatonic
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in the demo but you can use the major
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scale the minor scale
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or anything else and there's also
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keyboard support but it sounds really
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bad
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and i'll explain why later
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here are some things i learned while
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writing z music
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emacs has buttons which are great as
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long
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as you don't put two of them right next
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to each other so if you do that
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mousing over one of them highlights both
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of them
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now that's because a button is really
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just a series of characters with a text
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property to highlight them
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so the fix is you put another character
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between the two buttons
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then mousing over one of them only
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highlights the one you want
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but even this doesn't work really great
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for z music
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because the music has a lot of very
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small buttons in a row
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so it's really easy to accidentally put
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your cursor over the space
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and click on that instead of the button
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so i looked into unicode and i found
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this character called
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a zero width space so we should be able
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to put that between buttons and not be
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able to accidentally click on it
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unfortunately a zeroth space isn't
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actually zero width
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if we put a hundred of them between two
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other characters you can see there's
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space there
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and i think what's happening is the
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space is zero width
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but then emax put uses one pixel between
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each pair of characters
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for the cursor so it's almost zero width
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some ways to play sound that don't quite
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work play sound plays music
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but it blocks you can't do things like
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set other notes or even pause the music
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and if you throw it into async.el it's
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silent and i don't know why
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so the solution i went with is taking
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that wav file
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ran into the file system and then
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shelling out to a native executable to
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play the sound
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and that works fine as long as you only
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do it once
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because if you do it a couple times at
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the same time like if you have a chord
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and you want to play three notes
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simultaneously
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you get this weird interference and
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that's actually why the keyboard from
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before didn't work
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also side effects have this unexpected
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impact
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uh when you saw the demo it was running
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pretty smoothly
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but if i just add one message statement
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every beat for
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debugging purposes i was getting lag and
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jitter
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here's the one thing i learned about
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music theory music theory
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is not easy to program
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i was looking around to see what
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concepts we can use to code the scales
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to code the
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notes the first thing that i saw is
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scale degrees
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and this when i looked into it you don't
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want to program in scale degrees
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so you see we have the first second
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third fourth fifth sixth seventh but
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then it wraps around that octave up
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is also a first and that's because both
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of those notes are c
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uh so that didn't work and also you
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couldn't really easily
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specify a flat or sharp you could say
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a sharp third uh or
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you know a flat seventh or whatever but
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then you kind of have these two pieces
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of data that indicate the note and i
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didn't i didn't love that
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so i looked a little looked again and i
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found intervals
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and then i thought about it and you
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don't really want to program in
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intervals either
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it fixes some of the problems with scale
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degrees you see
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all the way on the right you have an
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octave so you wrap to 8 and you
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go 9 10 and that works but you solve the
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same problem you see you have a major
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third but below we also have a minor
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third so you saw that problem of having
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two pieces of information
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uh so i thought about it music's really
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frequencies like an a is 440 hertz
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so at a low level that's what we're
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going to do we're just going to use
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frequencies
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and then at the one level above that uh
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that's a little bit easier for humans to
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think about
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we're going to use semitones up from the
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root which is kind of like scale degrees
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but instead of just counting each note
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as one more we're going to say how many
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semitones up it is
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so if there's a sharp between two notes
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that's going to be two steps up instead
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of just one
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and then we translate those two
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frequencies so your a is 440 hertz
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another note might be
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613.5
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or whatever and we that's we use the low
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level to play
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some future work i have i want to add
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some drums
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i want to make that keyboard actually
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work uh
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and uh computers and synthesizers are
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the only place you hear a pure sine wave
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like the one we have here
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so i want to add overtones or other
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octaves above it uh just to make it
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sound a little bit more realistic
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i've put notes references in the source
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code up at zck dot me slash emacs conf
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2020 i'm one of the organizers of emacs
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nyc
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check that out and if you take a look
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or have any thoughts i'd love to hear
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them and
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thanks so much for coming to my talk
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