This is a question which I have been asked quite a lot of times so I've had a text-file prepared for quite some time......
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Creating backing tracks which are true to the original is a rather time-consuming task. What you need is a good sequencer program which also can handle wavefiles e.g. Cubase or, cheaper, Cubasis. (Possibly you might get hold of pirated software for free......................)
You also need a good soundcard compatible with the sequensing software with or without built-in synthesizer capabilities or an external synthesizer connected by way of midi to the soundcard if the soundcard lacks synthesizer sounds.
How I do:
1. Record the original music as a wavefile or expand a mp3-file to waveformat, preferably 44.1 khz.
2. Import this file into the sequencing software on an audio track
3. Try to align the wavefile with the tempo of the sequencer, this can be difficult and sometimes requires that the tempo changes at given points.
4. using a midi track, listen to the original bar for bar and try to pin down the bass notes correctly in both pitch and timing to correspond to what you hear (and sometimes see, as you can display the waveform of the original)
5. Do the same on another midi track (typically Ch 10) for the drums, try to find if there is a basic drum pattern in the song, copy that to the whole part, and enter only deviant fills and other ornamentation.
6. Same with rhytmguitar (also usually a fixed pattern which can be copied and altered only where it strays from the pattern. Make sure that the chords have the notes arranged as real playable guitar chords. Rhytm guitar is often the hardest to get to sound right,
so if possible record real rhytm guitar as a wavefile instead
7. Continue with strings, horns or whatever on separate midi tracks until the song is finished, why not also the lead part(s) even if I seldom do that myself, only when a complete midi is requested.
8.Choose synthesizer instruments for each part and start mixing and panning.
9. Add effects (reverb, chorus etc) to the separate tracks to your liking.
From here you have two ways to go
A. If you have within your sequenser (e.g. Cubase) the option to use software synthesizers (one good included in Cubase VST) and/or "cubase instruments", assign each track to a separate channel in the software synth and with the appropriate instrument. If so the adding of effects can sometimes be omitted in step 9. Instead you can in the mixing window mix, pan, add effects in the form of software plugins for each instrument individually and finally save the whole arrangement as a wavefile which can be put on a CD or compressed to mp3
B. You play the finished arrangement through the external or soundcard-based sequenser and record it at the same time as a wavefile.
The quality soundwise is very much dependant upon how advanced syntesizers you have at your disposal, and the degree of likeness to the original is of course dependant upon your ears and general musicality.
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