Audio and MIDI contain different information
An audio clip contains recorded sound. A MIDI clip contains performance instructions, including which notes to play and when. An instrument turns those instructions into sound. A MIDI track therefore needs an instrument or suitable routing to an external instrument before its notes can produce a pitched part.
This separation makes MIDI flexible. The same notes can be played by a piano, a synth or a sampled instrument. Their timing and pitch remain editable independently of the chosen sound. Audio offers a different kind of flexibility through editing, slicing and processing the recording itself.
The sample determines how much harmonic space remains
A mostly unpitched drum loop leaves room for a new harmonic idea. A loop containing bass, vocals or chords may already imply particular pitches. Even a tuned kick can influence how an added bass note is heard.
A natural minor is a convenient collection for a first original part because A, B, C, D, E, F and G use the white keys. Its usefulness is simplicity, not a special suitability for every sample. A pitched loop may call for a different key or contain chord changes that need individual attention.
Bass, chords and melody have different jobs
In the example below, A, F, C and G provide the bass roots. The triads add harmonic detail above them. A melody using E–C–A over Am and A–C–F over F can follow the chord movement while repeating the same rhythm.
The rhythm of those parts remains independent of the chord names. Long bass notes support the full bar, while shorter notes create gaps around the kick. A melody with a pause at the end leaves more space than a continuous stream of notes, even when both use the same pitches.
| Bar | Bass | Chord notes |
|---|---|---|
| 1 | A | A C E |
| 2 | F | F A C |
| 3 | C | C E G |
| 4 | G | G B D |
A pitched loop may contain more than one chord
A sample’s key label or an automatic analysis can provide a clue, but the whole phrase matters. A loop may change chords, include notes outside its main scale or leave its tonal centre ambiguous. One detected pitch cannot describe every harmonic event in it.
A bass note that fits the beginning may create a different relationship later in the loop. This is why a full-phrase comparison is more informative than checking only the first second. The level of an added part also matters: louder does not necessarily mean more harmonically suitable.
Small variations can develop an original idea
A four-bar phrase can gain direction through a changed final note, a missing chord attack or a brief bass movement before the repeat. These variations preserve recognisable material while giving the next repetition a different emphasis.
The MIDI parts can also be understood separately from the sample. Their relationship does not have to sound like a finished arrangement on its own, but the bass, chords and melody should have a reason to coexist. Restoring the sample then reveals where its rhythm and register complement the new writing or compete with it.