WEBVTT
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Hi.
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I'm Zachary Kanfer, and this is waving
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at 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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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 of 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 signed integer, it's not consistent,
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and it's little-endian by default which
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is not the way I like to think about it.
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Now, you can
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set a WAVE file to be big-endian,
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but if you do that,
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Emacs can't play it.
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So, little-endian it 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 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. If you just
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take those measurements, those numbers,
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put them in a file,
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that's all your data 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 zmusic 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 zmusic 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.
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So, we can stop it,
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and now we can click to add some notes.
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[Music]
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Even more than one note at the same time
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works.
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[Music]
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And we can even add notes
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while it's playing.
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[Music]
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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.
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We're 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.
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And there's also keyboard support,
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but it sounds really 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 zmusic.
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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 zmusic,
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because zmusic 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 zero-width 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 Emacs `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 WAVE 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 of 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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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 notes,
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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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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 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 love that.
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So, I 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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So, I thought about it. Music is 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,
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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 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,
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and 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 just to make it
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sound a little bit more realistic.
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I've put notes references and the source
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code up
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at zck.org/emacsconf2020 [updated].
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I'm one of the organizers of EmacsNYC
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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.
