GUS Programmer's Digest Wed, 22 Sep 93 0:07 MDT Volume 4: Issue 15 Today's Topics: perc pat madness Standard Info: - Meta-info about the GUS can be found at the end of the Digest. - Before you ask a question, please READ THE FAQ. ---------------------------------------------------------------------- Date: Tue, 21 Sep 93 3:23:52 CDT From: chuth@lonestar.utsa.edu (Cornel H. Huth) Subject: perc pat madness Message-ID: <9309210823.AA05950@lonestar.utsa.edu> > Well, I don't have ready access to the FTP archives at the moment, but I > did take a look at several percussion patches. In every case, both the > high and low frequencies were set to match the MIDI note that corresponds > to the GM mapping of the percussion. For example, highq points to D#1, > slap points to E1, scratch1 points to F1. Actually, these notes are an > octave lower than they should be. OK (for later reference). > In some cases, the root frequency is set exactly the same as the low and > high frequencies, and sometimes it is different. Do the MIDI interpreters > in playmidi, ultramidi and the Windows drivers use the root frequency at > all? I don't think so. I think that they simply play back the sample at > the specified sample rate whenever that perc patch is played. I do. The root is used to properly pitch-shift (awk). It is a factor in the calculation as is: the desired pitch (obviously; I use the low freq for drums)), sample rate, and tune. That's just for the FC calculation. Also, you have to take into account the GUS hardware requirements such as the number of active voices. I perform that task at a lower level. FM vibrato also comes into play (for a much more realistic sound if you ask me) for those instruments that need it and software that supports it. As for the software you mentioned, without the source, or at least docs, there's not really any sure way to know what they do. > What does the root frequency mean for a percussion patch anywhay? Most > percussion sounds have no definte pitch. I assumed it was the base frequency at which the sample is for. I don't know how to relate this to your last sentence. I can say that the pitch can be shifted and it will shift if the root differs from the low/high freqs (that is, if you don't simply ignore the root). The many perc patches that don't even include the root in their range threw me a curve. Anyway, I now use the low freq as the freq to play, for all drum samples (I had been using the root). It makes no sense at all for the low/high freq to be different than the root unless it is indeed the freq to use. So use it I shall unless/until I know better. > The way that the Gravis perc patches are set up means that you cannot use a > patch on a different MIDI note. F. Dion got around this limitation by > making the low and high frequencies cover the whole keyboard in his TR-808 > drum patches. You can put his drum patches on any MIDI note. In a MIDI stream, if a key# (note) is sent on the drum channel, that key# is interpreted as a drum sound (and not a note). There's no way that I know of to send a note on the drum channel (the key# being used as a drum index, instead). So, where's the note info to even do what you suggest in the paragraph above? > > What I think is that the root frequency is ignored. The sample is played > at the sample rate indicated in the patch header when a MIDI note is played > on channel 10 that matches the note number in the .cfg or ultrasnd.ini file > and also falls in the range of the low and high frequencies. I don't think > that any pitch shifting occurs for perc patches. If so, when and how much? Like I said in the last SDK-DIGEST, the pitch shift is accomplished in the same manner as on a melodic sample. And like I said somewhere up in the tangled mess above, the root freq is used in the calculation to derive FC. Well, at least I use the root. And, to tell the truth, I'm very pleased with my results. Tickled pink, you could say. ------------------------------ End of GUS Programmer's Digest V4 #15 ************************************* To post to tomorrow's digest: To (un)subscribe or get help: To contact a human (last resort): FTP sites: archive.epas.utoronto.ca pub/pc/ultrasound wuarchive.wustl.edu systems/msdos/ultrasound Hints: - Get the FAQ from the FTP sites or the request server. - Mail to for info about other GUS related mailing lists (UNIX, OS/2, GUS-MIDI, etc.)