Portamento in a MIDI file

[jazzcat]

I used to know how to do a portamento within a MIDI file. I even created a MIDI file to demonstrate it but it, along with an awful lot of stuff, due to a hard drive failure.

John, would you please either give me a step by step how to or create a simple MIDI file demonstrating portamento using CCs and data entry. Ya know how it is, if ya don't use it ya lose it!

I've also forgotten how to extend pitch bend range. Arrgh!

[JohnG]

Hi Cat,

Nice to see you about. Hope things are okay with you?
Yep, use it or lose it!
I'll knock up a tutorial over the weekend and post it here.

But the essence of portamento is to switch it on or off using cc#65.
The time it takes to slide from note to note is set using cc#5.
Off the top of my head I seem to recall that cc#5 needs adjusting depending how close together the notes are and the effect required.
Of course, VST instruments may not necessarily do it this way.

Pitch bend "sensitivity" is set using a pair of RPNs (LSB, MSB) followed by a data value corresponding to the number of semitones required.
The MIDI default is 2 semitones, but most devices should go up to 12. i.e. an octave in either direction.
So, to set the RPN to pitch bend, set CC#101 (MSB) then CC#100 (LSB) to zero.
Then the 'coarse' bend in semitones, using CC#6, set to e.g. 12 for an octave.
Don't forget to set it back again to 2 at the end of the song.

That may be enough to jog the memory, but I'll put a more detailed post in a little while.

We moved to the UK (from Germany) in November '13, and have just about got ourselves sorted out.

All the best.
Kind regards,
JohnG.

[jazzcat]

Thanks John.
I'm beginning to think the cheap chip on the motherboard of this P.O.S. Dell Omniplex machine I'm using doesn't support portamento.
I inputted 2 notes, on bar 2, and one 2 octaves up on the next bar.
I then went to the events list and inputted CC 65 and set it for 127. I then inputted CC 5 and tried setting it at 95, then played the file. Both notes sounded at time time periods as inputted. No glide up. I also tried setting CC 5 at 10, and still nothing.
I also tried switching the time inputs on the CCs. they are just a few tics apart, and again it didn't work.

I'm cool with setting the range of pitch bend now. Your refresher got me back on track!

Maybe you could create a portamento test file and make sure it works on your sound card, as opposed to any VST's you use, and send it to me.

[jazzcat]

Someone on the 'Midi Hangout board' found a mess of posts on the old Midi Mart board regarding portamento. A heck of a lot of of is you, John, talking and teaching. You might want to run over and 'steal' your own words and bring em over here!

midimart.proboards.com/search/results?display_as=0&what_at_least_one=PORTAMENTO&who_only_made_by=0

The subject line of the original post is:

Portamento CC and value help bit the one that shows at the top is different so just scroll down.


Looks like there is another controller involved. Portamento Control (CC 84)

You really got into it with a graft as well for calculating the time in milliseconds of a slide.

[JohnG]

Hi Cat,

That was a good reminder for me. I kinda remember posting the graph from the GM2 specification.
My! That was a while back. June 2008.
Much water under the bridge, and so on.
Yup, I think I'll do a bit of copy and paste to redo the tutorial over here.

So to summarise:
Set cc#5 to define the timing of the slides between notes. Try a middle value to begin with.
This will need changing depending upon the distance between the notes and the amount of variability required.
As one won't want it on all the time change cc#65 between 'on' (64-127) and off (0-63). Best practice to use 127 and 0, I suppose.

I'd quite forgotten about cc#84.
Normally the slide is from the previous played note, especially e.g. a steel guitar.
CC#84 is required to define a slide from a non-played note, like a violin sliding up to a note where the initial note is not played.
CC#84 corresponds exactly to the MIDI note number of the unplayed note. e.g. to start from middle C, cc#84 would be 60.

Lastly, and I think this may be critical, the MIDI specification for GM2 says that the channel must be in "Mono Mode"!
That means playing monophonically. I think it's called Mode 4.
Certainly, when I look at one of my VSTs, it confirms that legato must be on before a channel will respond to portamento.
The legato controller effectively puts the channel into mono mode temporarily in order to remove the attack portion of succeeding notes in a phrase..
Now, many synths I've played with (not a lot) go into mono mode when you use the legato controller, cc#68 in a channel.
This may be the missing ingredient you need, Cat!

And, I'm guessing that it will vary from device to device, depending just how the manufacturer has interpreted the specification.
It probably means that if you want a steel guitar both playing chords and being able to slide, you may have to spread it across several channels. But it looks like a combination of several controllers being used in combination.
No wonder most people use pitch bend!

Any further help?
I'll try to find some time to put together a MIDI file for you.

Kind regards,
JohnG.