What exactly does velocity mean?

[charlie]

Hey John,

Since you're the midi authority here at Midi Mart I couldn't think of anyone more qualified to answer this question: "What does velocity mean?" I'll tell you how I use velocity changes and see if it makes sense to you. When I come across a midi file that all the volume levels are at 127 but I still need to increase a volume level, mostly on channel 10 for drums, I increase the velocity. Now when I do that sometimes the hi hat and cymbals become way too pronouned in the mix, and so I usually give up on that midi file as I do not know how to increase the drum level any other way. I suppose I could decrease the volume on all the other patches and then maybe the drums would be more out front in the mix....hmmmm...haven't tried that...might be on to something. Anyway, maybe you could explain velocity to me in a way my thick head can grasp it. As always, thanks for all your help and expertise.

Thanks!

Charlie

[steveb]

Volume and velocity are two separate issues,
Now Cat and John wil most definately help you further with this one, but "velocity" is :how hard the note is hit.
By having too much velocity the midi will sound somewhat distorted.
A setting around 90 to 110 is a good place to start for velocity.
Over to Cat & John and the rest of the team.

[jford]

Well, this is a different "John" answering, but maybe I can explain. Velocity and volume are related, but aren't the same thing. At it's basic level, velocity refers to how "hard" the note is hit. Obviously, the harder you hit a note, the louder it is. But MIDI volume really has more to do with the overall level of the song. Think about it in terms of a a touch sensitive digital piano. Or better yet, an electric guitar (since you play guitar). Pluck a string lightly and the sound is softer and not as loud; pluck it hard and it's louder, but it's also a completely different sound than the soft plucking. Well, MIDI tries to do some of the same thing. That's why a particular (not necessarily all) instrument sounds different at different velocity settings. But now, reach over to your amp and turn up the volume and pluck the string softly. It's the same soft sound, only louder (because the amp is louder). Pluck it hard and you get that completely different kind of louder sound (but because the amp is set louder, it comes out a lot louder).

Sometimes in MIDI, it works better to lower the other tracks' velocities and then just turn up the overall volume to achieve the affect you are looking for.

Also, different MIDI sound sources handle those velocities differently. For some, you may not hear a difference at all at low versus high velocities. Other sound source try to more closely emulate the actual instrument, so you will tend to get that harsher, louder sound at the higher velocities, and the softer, smoother sound at the lower velocities.

I usually try to set my velocities centered around 90 or so. That gives me 37 more (up to 127) to play with. If it sounds wrong at the higher settings, I might just lower the other tracks to around 80 and then just up the overall volume.

Hope that made some sense.

[thingyy]

Also use controll 11 expression.

[steveb]

Excellent analogy, very informative, but what else would you expect from the gurus on this forum.

[charlie]

Wow! Thanks John and everyone who helped me understand this velocity thing. I wasn't aware that there such a thing as "digital" distortion, but now that you've mentioned it I believe that I have heard this phenomenon. What I have discerned from the replies is that if I want to have let's say drums more out front in the mix I could lower the volume levels of the other instruments which in effect would make the drums more pronounced. Velocity changes have to do with attack and not level. Striking the keys harder or softer, hitting the snare softer or harder changes velocity and not necessarily volume. In midi files then, in order to prevent digital distortion, I should refrain from increasing levels to 127. Rather, should I drop levels of the other instruments, balance the mix, and then turn up the output of the sound module or input level on the mixer? I hope I don't come off sounding like a dufus about midi files. I am primarily a live performer using midi files as my format. It does sound like I need to get more familiar with midi in general. Bare with me as I try and educate myself, with your assistance...of course.

Thanks everyone!

Charlie

[JohnG]

No problem at all Charlie,

How d'you think I got to know most of this stuff? Trial and error mostly. Yea some study and an engineering background help a lot, but mostly trial and error. You are now where I was several years ago.

My general rule when using an external sound module is to run it with the volume full up! Yea maxed right out. If it's a halfway good unit this will give you the best signal to noise ratio. In other words the sounds you're playing will be so much louder than the inherent noise generated by the module itself, you will be unable to hear the noise. With my setup the output of the sound module goes to the input of a mixer. I turn up the gain on my loudest MIDI file till the "level set" LED starts to flicker and then back it off a little. The LED just very occasionally lights. Then I use the channel faders to balance the live mix getting those around the 0dB mark give or take a few dB. The master volume control then controls the level to the PA.

Then I adjust the MIDI files, tweaking individual channels' volume, to give me the best performance.

Velocity will change attack and level. e.g. blow harder into a wind instrument and you not only get a faster start to the volume envelope you also get a higher level to it too. Press a little harder and bow a stringed instrument faster and you get the same. And of course the harmonic content changes too so it's like raising the frequency on a low-pass filter. If that makes any sense?

So try altering the levels of the various tracks to "around" 100 and then maybe push the drums up a bit, but don't overdo them. If you can't get them high enough then you have to look at velocities. You may have to do that anyway. Remember the time taken getting the file "right" will pay huge dividends when you're playing the gig. It really can make the difference like between karaoke and playing with a band. Well, nearly. The more time you spend tweaking the simpler the whole process will become. Also try making multiple file copies in case something gets messed up along the way.

JohnG.

[thingyy]

I try to have drums and bass at 118 [final volume] My strings are weak so this gives me leeway to increase them in the mix.

[JohnG]

Yea, whatever works for the (virtual) sound module or whatever you use.

I guess that sort of level will be pretty close to the maximum output of the unit.
Or do you run it with the volume control turned down a bit?
JohnG.

[thingyy]

Volume on the sound module 7 [max 10].
Amp volume is the only one I alter during the gig.I have pegs in the sliders of the equaliser so it can't be altered accidently.

[JohnG]

Aha, thought so!

With the sound module volume turned down to 7 you have had to turn up the sounds themselves to compensate. If you had the module at 10/10 then you'd probably find the drums and bass overloading the output stages and you'd then have to edit the channel volumes down a bit probably much closer to 100.

The reason why I run this way is compatibility with my SW1000XG sound card. There isn't a volume control to turn down, so effectively it's at 10, so I have to make sure the SMFs I create are compatible with that. 100 also happens to be the MMA recommendation and what a sound module should default to after a GM reset. Both my Yamaha and Roland modules do just that.

So each to his own!
JohnG.