I have not tested this but because the thud doesnt happen repeatedly and is affected by envelopes possible offset bias in the sample?
This "puzzle" got my curiosity, so I am taking a look. Here are the steps I am using (probably what you used, but as long as I am doing it, I will spell it out in case others are interested):
Note: I am using the audition riff
1. Identify what ROM instruments are being used.
---> 0347 bas:Sonics on L1 and L2
2. Identify which layer(s) has(have) the thud/click.
---> L2
3. Check the L2 parameters one by one.
-->(a) Sound [Sample] Start looks promising.
----->at Start = 16, the thud/click/pluck is mostly gone.
----->at Start = 28, it is gone even more,
------->but still there for the start of the phrase (riff).
----->at Start = 48, it is gone even more.
Hypothesis: The click/thud/pluck is in the ROM Instrument (sample).
-->(b) Interesting: L2 Filter (HPF) differs from L1 Filter (LPF).
----->Thud/click/pluck is present with some filters and not others.
----->With HPFs, raising the Freq gets rid of the low end (non-click)
----->With LPFs, raising the Freq adds the click.
Conclusion: The click/thud/pluck is in the sample
Corollary: You can get change it by modifying the sample start and filter settings.
4. I changed the L2 ROM Instrument (bas:xxxx at 1st and then others). Got some interesting attacks with other samples on L2.
5. To see if there were patchcords involved too, I started turning the source controller to off in each patchcord.
--> (a) L2 cord #08 is interesting
------> VEnvSus amount also affects the amount of thud/click
Anyhow, I hope this helps explain what seems to be going on in this patch.
Steve
PS: Somewhere I wrote about taking apart an organ patch. I will see if I can find that as I found the process very insightful. Will try to start a "Deconstructing Presets" index point.
--- In xl7@yahoogroups.com, "Ricard" wrote:
>
> Playing XL-7 preset 21:2 (bas:Sonic), there's a 'thud' at the start of the sound which however is only present if the sound hasn't been played for half a second or so. That is, when playing a continous melody, the ';thud' is only heard at the beginning of the melody.
>
>; It seems the 'thud' is present already in the basic waveform (instrument) used, and somehow it sounds like the START parameter is modulated somehow. For instance, one way I guess would be if the auxilliary envelope were set up in such a way that it would advance the START parameter (due to a long release) if a note were repeated. However, I can't find a patch cord which actually does this, and the aux envelope doesn't look like it's doing anything in this patch.
>
> Has anyone managed to figure out why this patch sounds the way it does?
>