MP4s are an mp3 with video.  Pretty much the same audio quality as mp3, but most likely they work well with Pierre's mixing software or maybe because it's an especially common video format.  It's one of the ones youtube takes.

@Oliver:  What I actually said was that midi files "contain no audio".  They are more like the paper roll for a player piano than say a reel to reel recording tape.  How a midi to ogg or whatever converter usually works is it plays back the midi file using sounds your soundcard can generate, and makes a recording of that.

Where midi can shine a lot better is if it is used to run a sampler so the "instrument" it is playing is a set of high quality recordings of notes/sounds that were originally from real acoustic instruments.

Whether midi files contain *music*, well, there could be some debate on that.  LOL  I'd say it depends on who uses them and how well.

@BillyG:  Hmm.. Digital as the poor man's approximation to analog?  Well, yeah, that is one of the things it can do.  But where it can get kinda deluxe is when you consider exactly what part of analog we can be approximating.

This is a pic of my trusty dusty old midi controller/keyboard.  It wasn't very expensive, I paid maybe 150 USD for it back when it was brand new.  It makes no sounds of it's own, all it does is control midi parameters.  

That alone would really be useful enough.  I can hook it up to even my old laptop, load up a "virtual instrument" on the computer, and then play it with the physical keyboard.  Full sized keys, velocity sensitive, and I can use the sliders and knobs to run any sliders or knobs that are on the computer screen, instead of having to mouse and click and drag.  Maybe no perfect, but I've had worse times. LOL

Synthesized voices? Well sure. But no worse than an old DX7 or a Fairlight or a Moog or a Prophet or a combo organ.  Or a zillion other instruments that I would have to save up my violin and guitar string budget a looooong time to afford even one of.  So "poor man's"?  Heck yeah!  

It can definitely be good enough to play on live at a gig.

But there's more.  Say I've recorded several tracks of analog instruments with some digital multitrack software.  See the knobs and sliders and etc on that keyboard?  I can assign them to control the sliders in the software, so I can do my mixdown with real world knobs and sliders, instead of mouse clicks and drags. 

An there is still more.  If I use one or more automation tracks to have the midi record my slider and knob moves?  It can repeat the nuances of me "riding gain" or tweaking eq or effects and be playing those adjustments back while I work on other adjustments.  Poor man's automated mixing console.  Real world, real time control of the DAW or recording/mixdown software.  Mmmm..

Or I can use it with something like digital guitar rack software to control emulations of a whole rack of effects and amp stacks and speaker cabinets.

Lot's of possibilities there which would usually take a big budget to do without midi.  

Now, what you say about even when "humanized", the midi synth voices being easy to tell from real players.. Well, true enough, in it's way.  If you use a simple midi editor to plunk in some notes, yeah, it won't usually sound very convincing.  But use the midi to record the actions of your playing on a midi keyboard, with the assorted knob tweaks and pitch and volume wheel and pedal work you'd use in real playing?  In real time, without "quantizing" it or "humanizing"?  It can be at least pretty darn convincing.  I *think* I could tell the difference between an audio recording of me playing live and an audio recording of my midi setup playing back something I just played.  But I wouldn't want to bet the rent money on it.  LOL

 Midi can be very useful for the things it is good for.  Sounding good all by itself for playing music without any digital instruments to control other then the boops and beeps of a soundcard just doesn't happen to be one of those things it is good for.  LOL

All by itself, it is *maybe* good enough to use as a 'scratchpad" to get down a basic idea or hear how some notes will harmonize or doing a very limited backing track for practice.  But listening to it just "raw" like that, yeah.. Not likely to fool anybody into thinking they're hearing actual musicians/instruments.

I wouldn't say your remarks are all that negative MadBill.  I went off into a bit much detail perhaps, for folks here who might be less aware of what midi can be good for. 

It keeps getting mentioned like it is an audio format, when it is a control format.  To criticize midi's sound quality is rather like the example I already made, of a player piano roll.  Sound quality would have to come from the piano the roll is put in, not the roll itself.  I think the confusion arises because most computers can "play" a midi file in a limited way, so some folks may think of it as a sound recording rather than a list of instructions.

Ah, the ESQ1?  I spent some time on it's older sister from Ensoniq, the Mirage.  Great sounding gear.