Instrument + instrument

Goal

Make two elements coexist when they share frequencies, timing or stereo space, before building the whole mix. The critical pairs decide half the quality of the mix:

• Kick + 808/bass (low end)
• Snare + clap (backbeat layers)
• Lead vocal + doubles/backing vocals
• Vocal + guitar/piano/harmonic synth (1–5 kHz region)
• Pad + lead (mids and highs)
• Guitar L + guitar R (double-tracked)
• Hi-hat + percussion (highs and rhythm)

Step-by-step procedure

1. Listen to the pair on its own, at a realistic level

Bring the two elements to the relative level they will have in the mix (e.g. 808 and kick similar in perceived loudness; doubles 6–10 dB below the lead). Question: does one of them disappear? Does the low end become uneven? Does the sum sound thinner than the individual sounds?

2. Phase and polarity

• Layers (snare + clap, kick + sub, two kick samples): align the attacks to the sample (zoom in Edison or in the Playlist), then try polarity inversion on one of the two (Fruity Phase Inverter or the mixer track's polarity button): choose the combination with the most body and punch.
• Kick + 808: if the 808 starts together with the kick, check that the two waveforms don't cancel in the first cycles (a sum weaker than the kick alone = a problem). Solutions: polarity, shifting the 808 by a few ms, shortening the kick's tail, sidechain.
• Vocal doubles and double-tracked guitars: they must be different takes; align initial and final consonants within 10–30 ms (VocAlign, Melodyne, editing).

3. Pitch

• Kick and 808 tuned to the key (or the kick to a compatible note, often the root or the fifth). If the kick has a fundamental at 55 Hz (A) and the 808 plays F (43.7 Hz), the beating can muddy the sound: tune or filter.
• Doubles and backing vocals tuned with the same reference as the lead.

4. Hierarchy

Decide who leads in each region:

• Low end: who carries the sub (below 60 Hz)? Usually the 808 in trap/drill genres, the kick in house/techno (with bass above 60–80 Hz), split in rock (kick 60–80 Hz for punch, bass 80–200 Hz).
• Upper mids: the vocal has priority over everything in the 1–5 kHz region.
• Width: the lead in the center, the pad at the sides.

5. Separation: solutions in order of preference

1. Arrangement: different registers (piano an octave above the vocal, pad in a high inversion), complementary rhythms (the instrument plays in the other's gaps), fewer notes.
2. Sound design: shorter envelope (kick with a short tail to leave room for the 808), filter, choice of a less dense sound.
3. Complementary EQ: where one has the peak, the other gets a 2–4 dB cut with the same Q (e.g. kick +2 dB at 60 Hz → bass −2 dB at 60 Hz; vocal presence at 3 kHz → guitar −2/−3 dB at 3 kHz).
4. Sidechain or sidechained dynamic EQ (kick → 808 at 40–100 Hz; vocal → guitar at 2–5 kHz).
5. Stereo: different pan and width (only above 150–200 Hz).
6. Depth: one drier and in front, the other with more reverb and fewer highs.

6. Check the sum

• The sum must have more energy than either element, without excessive peaks in the shared band.
• Listen in mono: do both elements remain audible?
• Listen at low volume: does the main one stay clear?

Target values by pair

Practical examples

• Trap: short kick (decay 150–250 ms) with a 3–5 kHz click; 808 carrying the sub; 808 sidechained from the kick (2–4 dB, release 50–80 ms) or an 808 written so it doesn't overlap the kick.
• House: kick with 50–60 Hz sub; bass HP at 40–50 Hz with a peak at 80–120 Hz and ducking from the kick (6–10 dB).
• Pop: lead vocal + 2 doubles panned ±100% with HP 150 Hz, −8 dB, strong de-esser; backing vocals with a "thinner" EQ (−3 dB 200–400 Hz).
• Rock: two different rhythm guitars (different takes or amps) panned ±100%, a 2 dB cut at 3 kHz for the vocal.

Link with pre-production

If two instruments clash in every song, it's an arrangement and sound selection problem: in pre-production decide who carries the sub, who carries the presence, who carries the width, and record/program accordingly.

Common mistakes

• Solving everything with EQ (to the point of hollowing out both sounds).
• Misaligned layers that cancel each other.
• Excessive sidechain that makes the bass weak.
• Judging pairs at levels different from those of the mix.