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=== Hardware Envelopes === In addition to defining an envelope like the volume sequence "F E D C B A 9 8 7 6 5 4 3 2 1 0" in software like VTII or your ZX Spectrum program, the AY also has a built in feature to do this for you. It takes the channel and ramps the volume down from F to 0. What you're supposed to do, ideally, is make a sample with envelope enabled like this: ``` //00 | tnE +000_ +00(00)_ F_ ***************// Or, in case if you don't really like bare 'n pure envelope, like this: ``` //00 | TnE +000_ +00(00)_ F_ ***************// and then assign a speed in the envelope period column. It's the first set of blanks. ``` //00| HERE | .. | --- .... ....| --- .... ....| --- .... ....// The smaller the value, the faster the envelope will ramp down. The actual speed of this process is done using the formula Frequency = Clock / (16 * Period). It won't matter what volume you pick in the sample because using the envelope feature overrides any volume assigned and just plays F to 0 every time. Let's do a nice long fade out with a speed of 4096, which is 1000 in hexadecimal ``` //00 | 1000 | .. | A-5 .1.. ....| --- .... ....| --- .... ....// When we play that, it does a nice smooth ding. You'll notice we put a value of 1 in one of those blanks. Here we choose the shape of the envelope. This is where things get interesting. This chip has 16 different kinds of envelope shapes, but some are duplicates so it's more like 8. The simplest are the first four which start at F and go to 0 and then stays off at 0. You can also choose shape D to start at 0, go to F and stay on. Here's the full chart: ``` //0-3 \_______ 4-7 /_______ 8 \ 9 \_______ A \/\/\/\/ B \¯¯¯¯¯¯¯ C //////// D /¯¯¯¯¯¯¯ E /\/\/\/\ F /_______// ``` More modern AY tunes make heavy use of shapes 8, A, C and E because they repeat and the period can be made small enough and fast enough to reach the audible note range. Or in other words OSCILLATE. We now magically have another melodic channel! You can use the shaping alone to make a single note with a sample tnE. VTII has an easy way to input the period column automatically. Just to the right above the pattern editor, you'll see "AutoEnv" and 1:1. Press the AutoEnv and when you input notes, it'll automatically try to match the frequency (sometimes it'll be out of tune). You MUST have somewhere on or above the current line an envelope shape of 8 A C or E or this feature won't work. You also need it defined on the current line to play or else it'll use the same period as the last time you defined it. A simple saw bass note using tnE would be a good start (by the way, you don't actually need to specify sample 1 because VTII always assumes a blank spot means that, at least on the start of the track): ``` //00 | ..7C| .. | A-1 .8.. ....| --- .... ....| --- .... ....// When you use TnE you WILL have both frequencies playing at once, and since the tone will follow the ramp of the env, you'll basically achieve ring modulation. Try the previous example with a TnE sample to hear this effect. If you are not familiar with ring modulation then you've got a chance to learn it all! You can play around with that 1:1 below AutoEnv and change the ratios. You might also want to try placing a note with AutoEnv, then turning it off and changing the octave of the tone. Or even the note to something different entirely! Oh, and in case if you don't really want to get along with the AutoEnv feature (or if you opt to use pure envelope), that's where Vortex Tracker II Improved kicks in - the envelope amounts are typed in and shown (optionally) as actual notes, which makes the whole process a whole easier! Keep in mind, though, that custom envelope digits cannot be added up here - you might need to fiddle around with transposition (which now works for envelopes, too!).
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