diff options
Diffstat (limited to 'demos/scratch_tutorial.htm')
| -rw-r--r-- | demos/scratch_tutorial.htm | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/demos/scratch_tutorial.htm b/demos/scratch_tutorial.htm new file mode 100644 index 0000000..c26c22e --- /dev/null +++ b/demos/scratch_tutorial.htm @@ -0,0 +1,93 @@ +<html> + + +<head> +<title>Vinal Scratch Tutorial</title> +<meta name="GENERATOR" content="Microsoft FrontPage 3.0"> +</head> + +<body> + +<h1>Vinal Scratch Tutorial</h1> + +<p>This sound reminds me of the effect of dragging a needle across a vinal record.</p> + +<pre>(defun ring (dur pch scl) + (let ((modstep1 (hz-to-step (* (step-to-hz pch) (sqrt 2.0)))) + (modstep2 (hz-to-step (* (step-to-hz pch) (sqrt 11.0))))) + (stretch dur + (mult + (env 0.05 0.1 0.2 1 0.6 0.24 1) + (fmosc pch (mult + (pwl 0.07 1800 0.15 1000 0.4 680 0.8 240 1 100 1) + scl + (osc modstep1) + (osc modstep2) ))) )))</pre> + +<p>The following plays an example sound from this function:</p> + +<pre>(play (ring 7.1 (hz-to-step 1) 1.2))</pre> + +<p>Here is a brief description of how this function works: The sound is created by an FM +oscillator. The modulation comes from two sinusoids operating at low frequencies +multiplied together. The sinusoids are not harmonically related, so an irregular pulse is +generated by their product. This is scaled further by a piece-wise linear envelope that +adds more variation. To make the sinusoids inharmonically related, their frequencies are +scaled by the square root of 2 and the square root of 11. The variables <code>modstep1</code> +and <code>modstep2</code> are initialized to these computed frequencies.</p> + +<p>The following example combines several instances of <code>ring</code> with different +parameters:</p> + +<pre>(play (sim (scale 0.15 (at 2.9 (ring 7.1 (hz-to-step 1) 1.2))) + (scale 0.175 (at 4.9 (ring 5.1 (hz-to-step 2) 1.414))) + (scale 0.2 (at 6.9 (ring 3.1 (hz-to-step 4) 1.8))))) +</pre> + +<h2>Other Sounds Using Ring</h2> + +<p>The same <code>ring</code> function can be used to achieve other sounds. Listen to +these examples:</p> + +<pre>(play (sim + (scale 0.35 (at 1.5 (ring 4 1 1))) + (scale 0.325 (at 4 (ring 4 4 2))) + (scale 0.3 (at 7.5 (ring 4 10 4))) ))</pre> + +<p>These instances use a higher pitch parameter than the previous ones.<br> +</p> + +<h2>Another Related Sound</h2> + +<p>The following creates a sound using FM and a wave table derived from a vocal sound.</p> + +<pre>(defun vocrap (&optional (pch 16) (dur 1)) + (if (not (boundp '*voc-table1*)) (mk-voc1-table)) + (fmosc pch (stretch dur (pwl 0 3 0.1 -20 0.2 20 0.3 30 + 0.4 -10 0.5 15 0.6 0 + 0.8 -30 1 60 1)) *voc-table1*))</pre> + +<p>This function uses a special test to make sure that <code>*voc-table1*</code> is +initialized. If it is not, it would be an error to read or test it, but you can query to +find out if the variable is bound or unbound. (Global variables become bound when you +assign a value to them.) The <code>boundp</code> function takes an atom (note the use of +the single quote to denote an atom, the name of the variable, rather then the variable's +value) and returns true if the variable is bound.</p> + +<p>Here is the definition for <code>mk-voc1-table</code>. You might have to replace the +filename depending upon how your system is configured.:</p> + +<pre>(defun mk-voc1-table () + (if (not (boundp 'voc-snd1)) + (setf voc-snd1 (s-read "./test/voc1.snd"))) + (setf *voc-table1* (list voc-snd1 16 T)))</pre> + +<p>The following shows one way to invoke <code>vocrap</code>: </p> + +<pre>(play (seqrep (i 4) (vocrap)))</pre> + +<pre> +</pre> +</body> +</html> + |