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Subject: RE: EXP vs. LIN Lag

From: "Eric S. Crawley" <esc@...
Date: 1999-11-29


>I used to use an Emu mono series keyboard (4000) before I used their 4060
>poly kbd. It had a pot to sweep between linear and exp. glide shape. I think
>JH has documented just the glide portion of this circuit and it's floating
>around somewhere on Synthfool DIY.
Sounds very cool!

>It is a very musical and versatile setup. Exp provides equal glide time no
>matter what interval you play. It also sounds more natural to your ear, with
>that rate slowdown as you approach the final voltage. Lin is also good for
>certain playing effects.
This confuses me a bit. I think there are 3 types of glide:

-Linear: linear rate in volts/sec

- Exp: exp rate so the pitch "slows" a bit as it reaches the end point

- "Variable": This is what the Expressionist does. The rate changes to
make the glide ∗time∗ constant. It is still a linear glide but with a
slope that varies depending on the interval so that the glide time is
constant. I ∗think∗ that is what I said in my original message. It
certainly isn't exponential. I think it is useful but it still isn't quite
as musical as exponential glide.

Am I missing something here? Paul says he is going to allow continuous
control from lin to exp which is really cool.

I had the first ELP album on the CD player this morning and it is really
easy to hear the exponential glide on "Lucky Man". The glide takes its own
sweet time getting to the final pitch. I think the reason this is more
appealing is that singers tend to use "exponential glide" when sliding into
the correct pitch.

>I've asked Tony to consider adding interpolation
>tables to allow true exponential glide, and he's considering it for his next
>software update. Of course, I've also bombarded him with about 10 other
>requests, so I don't know what he'll manage to get in. For us modular users,
>it is maybe easier to just use a true analog lag circuit to get what we
Indeed, I think I've resigned myself to needing a lag generator instead of
relying on the MIDI/CV to do it.

>Another good use for exponential lag: input a gate signal, get an AR
>envelope signal out.
And if you can make it retrigger itself, it can become an LFO or a Pulser
in Buchla terms.