I suppose it depends on what you mean by “not an exact replica.” You’re probably breaking a rule somewhere, but exactly which one isn’t certain.
As far as I’m aware, music copyright is in several categories. First, you will see a © copyright to the music and/or lyrics, very often to a group rather than to a name. (Eg, Big Pig Music, which is Elton John’s previous label name, if I remember right). There may be an accompanying credit listing the actual authors of the song, but the copyright is often to the production company or writing team that owns it. This copyright will always appear with the music in any legal form, including sheet music, fakebook, guitar tabs, cassettes, CDs, vinyl, and as it is used in the end credits of a film or video. (“Rocket Man” © 19?? by Big Pig Music, used by permission from CBS records, etc.)
You will also see attached to some cassettes and CDs (or other audio media) a symbol of § that establishes rights to that particular audio production of the piece, indicating that someone owns the rights to that sequence of magnetic wavelengths, data bits, etc.
In addition, I have seen music denoted with further copyrights. You might see:
“Rocket Man,” words by Bernie Taupin, music by Elton John, © 19?? Big Pig Music, this arrangement © 19?? Kate Bush.
Basically, if someone writes a song with a particular chord progression and melody, and someone else records it a different way with the same chords and music, it’s still arguably the same song, held under the “words and music” copyright. Whoever created that particular MIDI arrangement would technically own the rights to that arrangement (but not to the song, necessarily), and you would own the rights to none of it, as far as I can see.
I have based this on what I have read from the International Copyright laws established late in the 20th century, which I haven’t read in a little while. I also understand there is a newer digital copyright agreement that covers things like files, software, etc., but I haven’t read it. Somehow I don’t think that simply using a MIDI file for which you do not identify an owner, and claiming it’s been modified a bit, will absolve you of the “words and music” copyright, regardless of what the digital copyright laws say. Whether you can find the author of that arrangement doesn’t get you off the hook with the original creator of the song.
That said, it is generally easier for the original owner to defend the use of the piece if it is a registered copyright. You may get in trouble with the original author, if he a) is a well-known artist, and b) he finds out about it, but the arranger would be hard-pressed to file a similar “unfair use” suit.
As always, take advice from a Fish with a grain of salt or a dash of lemon.
<8)))><