[CM] Cmdist Digest, Vol 167, Issue 4

James Hearon j_hearon at hotmail.com
Wed Apr 20 10:09:45 PDT 2022

re: portamento

Thanks.  I had experimented with amp envs, and overshoots and undershoots for durs but hadn't considered timbre or spectral changes.  I'll think about that.
From: cmdist-bounces at ccrma.Stanford.EDU <cmdist-bounces at ccrma.Stanford.EDU> on behalf of cmdist-request at ccrma.Stanford.EDU <cmdist-request at ccrma.Stanford.EDU>
Sent: Tuesday, April 19, 2022 9:00 AM
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Subject: Cmdist Digest, Vol 167, Issue 4

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Today's Topics:

   1. portamento (James Hearon)
   2. Re: portamento (bil at ccrma.Stanford.EDU)


Message: 1
Date: Tue, 19 Apr 2022 18:02:57 +0000
From: James Hearon <j_hearon at hotmail.com>
To: "cmdist at ccrma.Stanford.EDU" <cmdist at ccrma.Stanford.EDU>
Subject: [CM] portamento
        <BYAPR10MB2536279F4ADFE75D708A4AF5E5F29 at BYAPR10MB2536.namprd10.prod.outlook.com>

Content-Type: text/plain; charset="iso-8859-1"

I'm trying to come up with an approach to portamento note phrasing.  Best I've been able to do is work with gliss.  I'm wondering if this is on the right track for how this is usually handled?


(definstrument (myport start-time duration frequency start-freq end-freq (amp-env '(0 0 1 1 2 1 3 0)) sampling-rate)
  (let* ((beg (floor (* start-time sampling-rate)))
(end (+ beg (floor (* duration sampling-rate))))
(sine-wave (make-oscil :frequency frequency))
(ampf (make-env amp-env :duration duration :scaler 1.0))
(frqf (make-env '(0 0 1 1) :scaler (hz->radians (- end-freq start-freq)) :duration duration :base 0.67))
     (do ((i beg (+ i 1)))
         ((= i end))
     (outa i (* (env ampf) (oscil sine-wave (env frqf) )))
     (outb i (* (env ampf) (oscil sine-wave (env frqf) )))

(with-sound (:srate 48000 :channels 2 :header-type mus-riff  :play #t)
              (myport 0 1 300 300 400 '(0 1 1 .3) 48000)
              (myport 2 1.5 400 400 300 '(0 .3 1 .3) 48000)
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Message: 2
Date: Tue, 19 Apr 2022 11:33:08 -0700
From: bil at ccrma.Stanford.EDU
To: James Hearon <j_hearon at hotmail.com>
Cc: "cmdist at ccrma.Stanford.EDU" <cmdist at ccrma.Stanford.EDU>
Subject: Re: [CM] portamento
Message-ID: <6d4807c522ab6c39450fd9c424e81583 at ccrma.stanford.edu>
Content-Type: text/plain; charset=US-ASCII; format=flowed

I think in the context of sound synthesis, portamento
is a glissando between two notes.  It would be interesting
to get a vocal or violin recording of someone using
portamento, and try to imitate it -- I think you'll
also need an amplitude envelope.  Seashore wrote about
it, saying something like "it starts below the first
note and overshoots its target", if I remember right.
You might also need to change the timbre en route.


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