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Forums > C64 Coding > SID Interlaced Chord question
2023-04-29 03:54
ws

Registered: Apr 2012
Posts: 228
SID Interlaced Chord question

On a SID, musicians use the effect of playing chords on one channel by quickly altering the frequency of the note by playing for example C E G in rapid succession, mainly via a table/command. (Are they called arps, arpeggios?)

Is the interlace/arp being done by the driver in 50/3 hz? Or is it actually slower for some reason?

Are Tracks like the Armalyte Title tune using 50hz/3 speed chords or is the frequency of the note alteration actually slower? Is there perhaps a SID-side reason why a maximum speed of playing interlaced chords cannot be exceeded, or is the limit just cpu speed?

Did anyone yet make a driver that uses gliding arps/interlaced notes? Any Examples?

Do you have any outstanding/groundbreaking examples for songs that use unusual high chord note interlace rates, like a 3x speed Tune that achieves 50 hz or higher "interlaced" chords?

Thank you for any helpful insight!

[If this has already been covered in another thread please excuse, i didn't know what to search for due to my lack of knowledge of terminology]

ps.: can one of you coders make a demo where the axes of the sprite multiplexer are rotating?
 
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2023-04-29 11:28
Oswald

Registered: Apr 2002
Posts: 5017
Quote: Thank you, that was my guess. Any examples for deviations?

here is what SID sounds like when updated multiple times per frame

https://www.youtube.com/watch?v=UrPFVHc55KU

(not sure sid is updated here 8 or 16 times more frequent than 50hz)
2023-04-29 13:14
tlr

Registered: Sep 2003
Posts: 1714
Quoting ws
Are Tracks like the Armalyte Title tune using 50hz/3 speed chords or is the frequency of the note alteration actually slower? Is there perhaps a SID-side reason why a maximum speed of playing interlaced chords cannot be exceeded, or is the limit just cpu speed?

There is a _physical_ limitation if you want to still hear this as a chord. When the switching speed approaches a significant proportion of the frequency of the individual notes you will get frequency modulation effects which may not be what you want.

Assuming you only change the frequency this effect will be less and less prominent the higher the notes in the chord are.
2023-04-29 21:09
ws

Registered: Apr 2012
Posts: 228
@ everyone - thanks for the input, very interesting!

@ oswald - thanks for pointing me to that tune, which actually gave me real goosebumps!
2023-04-29 22:02
chatGPZ

Registered: Dec 2001
Posts: 11116
Quote:
not sure sid is updated here 8 or 16 times more frequent than 50hz

8-speed - just read the scroller =)
2023-04-29 23:17
Bansai

Registered: Feb 2023
Posts: 34
Quoting Frantic

Hubbard sometimes used a trick of alternating between fixed notes and a sliding note, which is one of the many components of his "sound".
The tricks various musicians did in their drivers to get their "sound" are interesting, especially when the trick used was quite simple. Russell Lieblich would use an incrementing sliding frequency detune of V1+=2/V2-=2/V3+=2 per frame that switched direction every 128 frames in order to get that twangy sound of his, for example, in Activision's Aliens and Transformers.
2023-04-30 20:14
ws

Registered: Apr 2012
Posts: 228
@Bansai: nice detail! I was never fully aware of that - now i can actually "hear it". Cool.

What i find also notable/interesting is how the arps/chords in Tigermission Subtune 3 stagger sometimes. I wonder why that is (actually some "staggering" is pretty prominent throughout the entire SID).
Accidentally triggered late sometimes? Could that easily be fixed?
2023-04-30 21:56
chatGPZ

Registered: Dec 2001
Posts: 11116
Isnt that just the ADSR bug?
2023-04-30 22:49
ws

Registered: Apr 2012
Posts: 228
Is it? I have no idea! Would love to know, though.

Would that stall altering of frequencies and delay the arp? (Would that be emulated by SIDplay3?)
2023-04-30 23:16
acrouzet

Registered: May 2020
Posts: 80
Quote: Is it? I have no idea! Would love to know, though.

Would that stall altering of frequencies and delay the arp? (Would that be emulated by SIDplay3?)


It is the ADSR bug, it doesn't stall the notes of the arp, only changes in its overall volume.
2023-05-01 01:32
ws

Registered: Apr 2012
Posts: 228
Thanks! Good to know - and finally i understand it, i only read about it out of the corner of my eye and had no real idea how it would sound like.

So, as far as i understand, for it to work properly, the driver would have to be changed to write some certain additional bytes a little bit later/delayed, on the occasion of a special event that is written to the SID?
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