Midi with tuned instruments?

[Nola]

Can anyone explain how to get a perfectly tuned midi instrument to sit with the naturally imperfect nature of real instruments?

e.g. my guitar has "perfect" intonation (technically impossible, but it's very close), yet it sounds out of tune with the truly perfect midi parts.

 

[SeaGtGruff]

A MIDI part is only as "truly perfect" as the instrument that's playing the MIDI part.

There are MIDI messages that can be used to adjust an instrument's tuning if needed, or (depending on the instrument) possibly even adjust the tuning of the individual notes of a scale. But for hardware instruments (e.g., keyboards and synths) it's usually simpler to adjust the tuning with the instrument's function menu if possible, rather than trying to do it through MIDI tuning messages.

And depending on the instrument, these sorts of tuning adjustments might not be perfect, since adjusting by a single value (i.e., plus or minus 1 unit of data) will change the tuning by some specific amount. For instance, even if you could tune "concert A" to 440.0 Hz, or 440.1 Hz, or 440.2 Hz, etc., you probably can't tune the instrument to frequencies between those particular values the way you can with an acoustic instrument. Also, electronic instruments can get out of tune.

In the end you still generally need to make sure all the instruments are in tune with each other. A rule of thumb would be to let the least-easily tuned instrument determine the frequency for "concert A," then try to tune all the other instruments to that frequency.

 

[rob aylestone]

The MIDI component is irrelevant here, it's just the communication language, but this really breaks down to the old discussion of temperament. So much depends on what the voice is. If it's a piano, or a harp patch, then even small differences in the intonation of the two will beat - and I guess this is your complaint? Patches with chorus, delay or phasing won't beat - so all the strings and section sounds will be fine. In real life, guitars can play with real pianos - so tuning is possible and obviously happens. If your keyboard piano is sampled, it probably has the slight detuning real pianos have, but if it's a cheaper piano sound that has it's pitch set by maths alone - then clashing is pretty unavoidable.

Just don't blame MIDI - it's blameless in this circumstance.

 

[SeaGtGruff]

Can you explain a bit about the situation, the gear, the software, etc.?

Since this is a home recording forum, I assume you're talking about making tracks sound in tune with each other, not about a group of performers who can get in tune before playing-- but if you're recording a performance, then that might apply, too.

As for gear, I'm not talking about your guitar, audio interface, mixer, etc., but rather any MIDI hardware you might be using. For instance, if you've got a MIDI file playing on a keyboard and you're recording the audio output of the keyboard, the keyboard itself (i.e., brand and model) will determine what sort of tuning functions it does or doesn't have, or whether it can or can't respond to any MIDI tuning messages, etc., so it would be helpful to know the hardware you're dealing with.

And as for software, knowing the DAW would be helpful so people having experience with that particular DAW might offer suggestions-- but more to the point, if the MIDI parts are being played by virtual instruments then knowing which virtual instruments you're using would be helpful. For instance, if you're using a particular soft synth then it may have some controls for adjusting the coarse tuning and fine tuning, or settings for adjusting the scale tuning, etc.

As far as general advice and suggestions that could apply to any situation, set of gear, and software, Rob's mention of chorus, delay, and phasing is helpful-- try adding a bit of chorus to the tracks to see if it helps. Otherwise, if you're going for an effects-free sound, listen to the tracks carefully for the spots where things sound out of tune and try to identify the offending part(s) and note(s), then see if you can better tune the guilty instrument or note at the source, or if tuning and re-recording isn't feasible then maybe try a bit of pitch-shifting as needed on the existing tracks.

 

[SysExJohn]

It helps to understand that most of the samples that a MIDI instrument plays will be tuned to ET (Equal Temperament).
Even if the samples weren't exactly correct to start with they're 'tweaked' to be correct.
Then it helps to know that ET isn't 'pure'.

Tuning is done using what's known as the 'circle of fifths', e.g. start at C and tune G above so that it's pure.
Then a fifth above G is D, tune that pure, and so on until all fifths are tuned and we arrive back at C.
Only that way we don't arrive at C, we find that we've overshot C by what is known as a Pythagorean comma.
(I shan't go into the reason why here, it would take too long!)

When you tune your guitar, you start from the low E string and tune that to a known E from your MIDI instrument.
Then you play an A on the E, and match the A string to it. You probably tune it pure.
Then play a D on the A string, and get that pure with the d string. Again you probably go for purity.
And so on up to to the top e.
(Or tune the A string to an A tuning fork, then get E close and go up as before.)

But this way tunes for purity and not for equal temperament.
It's usually necessary to flatten each intermediate string minutely (just as tiny amount), in order to make them more in tune with an ET keyboard.
They should sound just fractionally flat, to the string below.

E and e should be in tune, of course.
The fretboard, in a good guitar, should be pretty close to ET.

You might get greater accuracy in this way.

Any use?
John.