Who is using the various Tempo and MIDI functions in Pro Tools for sound design creation, and how?
Elastic audio, when working in samples, can be automated with tempo. Its not always the best tool for speed changes and such, but I've occasionally found it useful.
Sure thing. First, I should mention that I had a brain fart and your track's time-base should be thrown in to "Ticks" and not "Samples". Once in Ticks, open up some form of elastic audio (varispeed, for example) on the track. Drop the tempo ruler down, showing the green shaded area. Using your pencil tool, draw in some tempo automation- the bottom (or lowest BPM) being the furthest possible stretch, and the top being the smallest squeeze possible on your region. Once you've drawn in some automation, you'll see the region's length change accordingly. On the left side of the tempo ruler you can also change the resolution and density of the tempo- 50ms is great for really quick changes.
I use a good amount of the midi and tempo functionality in PT but it is usually when I am working on projects that blur the line between sound design and music composition.
Adam is correct about elastic audio. As a composer the tempo mapping scenes is critical and sometimes cumbersome when dealing with re-conforms. I personally avoid elastic audio unless I'm in a pinch to compress/expand a multitrack music session (non-midi) to a slightly different length.
Remember that tempo is a relative grid value unless working in "ticks" with elastic audio so it will not change sync of waveform audio in your timeline, it is not however a relative grid to midi data and changing tempo will indeed change it's absolute placement in the timeline (sync to pict in your case) by design. That's the advantage to midi in writing electronic music and such.
As far as using midi for true sound design goes you might try using the midi notation to easily draw patterns (random, arpeggiating, ascending, descending) triggering soft-samplers like kontakt to play sound samples of your desire. remember also that midi clips can be time-expanded and contracted with the TCE tool so you can quickly explore various speeds of your midi pattern triggering your sounds.
Working with the midi functionality also allows all the standard midi tools to automate (pitch bend, velocity, and my favorite the mod wheel)
In kontakt, or similar, you can assign all sorts of parameters to the mod wheel such as an LFO that is acting on the amp volume, then automate it's rate via the midi timeline and create stutter effects of longer sounds. That would be one example of a endless array of things you can do when working with midi to sound design.
Just made some down and dirty heart monitor beeps for a scene. The main character is in a hospital bed and has just come out of a coma. I used a couple instances of Structure, a single trigger for each that I region-looped, and then tempo-mapped subtle heart rate changes through the scene based on her reactions. Then re-recorded the output of each Structure track to new audio tracks. Quick and easy.
One thing to note, I did this in a new session and imported the recorded audio tracks back into my BG session as I didn't want it to throw off the sync of anything else in my main session.