Why do your MIDI files sound so different than others I have heard?
Is that really you playing?
These are paraphrases of questions I get quite often, and they actually answer each other to some regard. I will give the short version here. MIDI files, which I have largely abandoned but have retained on the site for legacy purposes, can be created in a variety of ways. The simplest method for a non-performing musician or non-pianist is to click the notes in to a sheet music or MIDI editor, allowing for a visual representation of what sheet music would look like. Unless some of the parameters are modified either globally or a per-note/per-phrase basis, the default is for each note to sound at the same volume for 80% to 100% of their time value. In other words, a printed whole note will be played for the entire four beats. The rhythm is also perfect as each note is played precisely where it should at a very fine resolution. Unless specifically entered there are also no variations or pianistic tricks. In essence, it is an exact performance of the printed music, but not how a pianist actually plays. There are some very talented sequencers, however, who do spend a great deal of time "humanizing" their work with varied dynamics, alterations in rhythms, variances from the score, pedaling, and other important details.
At the other end of the MIDI creation spectrum is the capture of an actual performance. The artist simply sets the recording device to record and then plays the piece. Within reason, every nuance of performance is captured, including tempo changes, variances in note velocity, pedaling, and all of those pianistic tricks that make for a vibrant performance. This is the methodology I use, primarily for the purposes of reproduction on a MIDI-enabled acoustic piano. It induces me to perform better as well since I tend to practice a piece heavily in anticipation of recording it. Some brief but judicious editing can excise unwanted artifacts or emphasize something that the recording keyboard was not able to convey. However, it is pretty much a live performance. There are a few artists left on the World Wide Web who use this technique, but the majority still either sequence in the notes or play a piece one beat at a time (Stop-Time Recording) as it takes less time and effort to edit. Some are able to translate this into fine YouTube videos that show the score as the piece is performed. Both methods have their practical uses, depending on what the final goal is. The preference for both creator and listener is, of course, individual in nature.
For detailed information on varying recording techniques and the pros and cons involved, please read my article on Using MIDI which was written to address all skill levels.