Tuesday, October 4, 2011

Prophet 5 Emulation

As you read through the AL-1 section of the Parameter Guide you'll see references to “a famous five voice American synthesizer” which can only mean the Sequential Circuit Prophet 5.  So how well does the AL-1 do?  Actually pretty darn good.  I documented below the few areas where there are differences.  I was able to re-create many of the original Prophet 5 programs.  A few presented a challenge and I have to admit, by the time I got to the last bank I wanted to move on to another project, so they got left out.

As you can see below, the waveforms of the oscillators are flipped around but the sync is flipped around as well, so if you're copying an original P5 program keep this in mind.

       PROPHET 5                  AL-1
OSC 1: Saw/Rectangle              Saw/Triangle/Rectangle
OSC 2: Saw/Triangle/Rectangle     Saw/Rectangle

There are other differences, like the fact that on the P5 you can have Saw/Tri/Rect all on at the same time.  That's not possible with the AL-1.  And the combination Saw/Tri is not available either.  Still, the AL-1 allows you to blend two waveforms whereas these are mixed at 50/50 on the P5.  There are also double and detuned saw waveforms on the AL-1 which don't exist on the P5.

When trying to re-create the Prophet 5 programs from Arturia's Prophet V, I found that the Edge parameter should be 0 or slightly negative.

While you can apply the filter envelope (or any EG) to Osc. 1/2 pitch, pulse width and filter, you cannot modulate the filter or pulse width with either of the oscillators.  It is possible to have osc. 1 modulate osc.2 (remember we're flipped in comparison to the P5).  Here's a related quote from the manual: 

"This feature is similar to a classic five‐voice analog synthesizer’s “Osc B to Freq A” function, except that the depth can be up to eight times greater–16 octaves instead of 2."

The AL-1 filter does not self-oscillate.

Envelope/LFO Values
Again, when trying to re-create the Arturia P5 programs I found the translation charts for EG (page 210 in the Parameter Guide) and LFO (page 216 in the Parameter Guide) to be very helpful.  If you mouse over any control on the soft synth it will display the value in ms/Hz.


Here is a PCG with re-creations of many of the original Prophet 5 programs.  I used the Arturia Prophet 5 as my source.

Prophet 5 Original Programs

P5 11 Brass             : Program U-G000 
P5 12 LowStrings        : Program U-G001 
P5 13 MutedClav         : Program U-G002 
P5 14 Perc E Piano      : Program U-G003 
P5 15 Flutes            : Program U-G004 
P5 16 Harpsichord       : Program U-G005 
P5 17 Sync1             : Program U-G006 
P5 18 PercussiveOrgan   : Program U-G007 
P5 21 UniGlide          : Program U-G008 
P5 22 Harmonium         : Program U-G009 
P5 23 OrganWithRes      : Program U-G010 
P5 24 ToyPiano          : Program U-G011 
P5 25 TrumpetFlute      : Program U-G012 
P5 27 ReedOrgan         : Program U-G013 
P5 28 BrassInFifths     : Program U-G014 
P5 31 PipeOrganFlutes   : Program U-G015 
P5 32 SyncII            : Program U-G016 
P5 33 Electric Piano    : Program U-G017 
P5 34 HighStrings       : Program U-G018 
P5 35 OctaveSawteeth    : Program U-G019 
P5 36 ReleaseRepeat     : Program U-G020 
P5 37 DelayedHarmonic   : Program U-G021 
P5 41 PulseWidthMod     : Program U-G022 
P5 42 SlowSyncSweep     : Program U-G023 
P5 43 4thsWithRes       : Program U-G024 
P5 44 SweepingHarmonic  : Program U-G025 
P5 45 SlowSync          : Program U-G026 
P5 47 SawtoothArp       : Program U-G027 
P5 48 ClangerousBells   : Program U-G028 


  1. thanks for the great article and patches!

    Mat Thomas of Jambodhi

  2. is the PCG still available, I am really interested! I right now get an error from dropbox when I try to load.

    1. https://www.purgatorycreek.com/index.php/prophet-5-emulation/

      Here you go. Everything has been moved to the website.

  3. This comment has been removed by the author.

  4. William, super, thx so much. Some great sounds there, Synch, UniGlide.