Recording Instruments
Recording instruments is about two decisions: how you capture the source (plugged in directly or with a microphone) and where you put the mics. Move a mic a few centimeters and the tone changes more than any EQ could. This lesson gives you proven starting positions for the instruments you'll meet most.
DI vs Microphone
There are two ways to get an instrument into your DAW:
- DI (Direct Input): plug the instrument straight in. You capture the pure electrical signal, with no room sound.
- Mic: put a microphone in front of the instrument, its amp or its speaker. You capture the instrument plus the air and room around it.
Electric guitars and basses put out a weak, high-impedance signal. Plug them into an interface input marked Hi-Z, Inst or with a guitar icon. A DI box does the same job when you need a long cable run or a mic-level input: it converts the guitar signal into a balanced, low-impedance signal.
| DI | Mic | |
|---|---|---|
| Sound | Clean, dry, sometimes thin on its own | Natural, with amp and room character |
| Noise & bleed | None from the room | Picks up the room and other instruments |
| Change tone later? | Yes, with amp sims or re-amping | Tone is mostly baked in |
| Best for | Bass, electric guitar (with amp sims), synths, keys | Guitar amps, acoustic instruments, drums, vocals |
When you mic a guitar or bass amp, record a clean DI track at the same time (most DI boxes have a "thru" output for the amp). It costs nothing and gives you a safety track you can re-amp or put through a plugin later.
Electric & Acoustic Guitar
Miking a guitar amp
The classic choice is a Shure SM57 (or similar dynamic) right up against the speaker grille, about 1–5 cm away. Shine a flashlight through the grille cloth to find the speaker cone. Where you point the mic changes the tone:
Mic position on a guitar speaker
Start halfway between the dust cap and the edge, pointing straight in. If it's too harsh, move toward the edge or angle the mic. If it's too dull, move toward the center.
- Moving the mic back from the grille (15–30 cm) reduces the proximity bass boost and gives a more open sound with a little room.
- Guitar amps sound best at the volume they're designed for, but the mic doesn't need it loud. Turn the amp down if the room is rattling.
- Many engineers add a second mic (a ribbon or condenser) on the same speaker. Check the phase between them (see below).
Acoustic guitar
A small-diaphragm condenser pointed at the 12th fret (where the neck joins the body on most acoustics), about 15–30 cm away, is the standard starting point. It captures the balance of string detail and body.
- Don't point at the soundhole: it's the boomiest spot and sounds muddy.
- Move toward the body (bridge) for more warmth, toward the headstock for more brightness and string noise.
- For stereo, add a second mic near the body (behind the bridge) or use one of the stereo pairs below.
Stereo Miking Techniques
Two mics capture a stereo image: left-right width and a sense of space. Each technique balances width against mono compatibility (how well it holds up when the left and right channels are summed together, as on a phone speaker or club system).
| Technique | Setup | Sound | Mono-safe? |
|---|---|---|---|
| XY | Two cardioids with capsules touching (one above the other), angled 90–135° apart | Focused, narrow-to-medium width, solid center | Very good |
| ORTF | Two cardioids 17 cm apart, angled 110° apart | Natural width, a good balance of image and space | Good |
| Spaced pair (A/B) | Two mics (often omnis) 50 cm to several meters apart, pointing at the source | Very wide, spacious, less precise center | Can suffer phase problems |
| Mid-side (M/S) | One cardioid pointing at the source (mid) plus a figure-8 sideways (side), capsules together | Width is adjustable after recording | Excellent: the side cancels out in mono |
Decoding mid-side
Many DAWs and plugins include an M/S decoder that does this for you. Because the two Side copies cancel when summed, a mid-side recording collapses cleanly to mono.
Drums: An Overview
Drums are the hardest common instrument to record because they're loud, wide and use many mics at once. A typical close-miked kit:
| Drum | Mic | Starting position | Captures |
|---|---|---|---|
| Kick (inside) | Dynamic kick mic | Through the port hole, 5–15 cm from the beater head | Attack and click. Closer to the beater = more click |
| Kick (outside) | Dynamic or large condenser | 15–30 cm outside the front head | Low-end boom and body |
| Snare top | Dynamic (SM57-type) | 2–5 cm above the rim, angled toward the center | Crack and body |
| Snare bottom | Dynamic or condenser | Under the drum, pointing up at the snare wires | Wire rattle and sizzle (flip its polarity) |
| Toms | Dynamics or clip-on condensers | 2–5 cm above the rim, angled toward the center | Tone and attack |
| Overheads | Pair of condensers (SDC or LDC) | About 60–100 cm above the cymbals, in XY, ORTF or spaced pair | The whole kit image and cymbals |
| Room | One or two condensers | A few meters in front of the kit | Space and size, great when compressed hard |
You don't need all of this. With only 3–4 mics (kick, snare, and one or two overheads) you can get a great, natural kit sound. Make sure both overheads are the same distance from the snare so it stays centered and in phase. Measure with a mic cable or tape measure.
Phase, the 3:1 Rule & Polarity
Whenever two mics pick up the same source, the sound reaches them at slightly different times. Sound travels about 34 cm per millisecond, so a mic 34 cm further away hears the drum 1 ms later. When the two signals are mixed, some frequencies add up and others cancel. This comb filtering makes the sound thin, hollow or phasey. Review the basics in What is Sound?.
The 3:1 rule
The 3:1 rule says: when two mics record two different sources, the distance between the mics should be at least three times the distance from each mic to its own source. That keeps the bleed in each mic at least about 9 dB quieter, which reduces comb filtering.
3:1 rule in practice
It's a guideline, not a law. Always check by listening, especially in mono.
Polarity flip
Polarity is whether the waveform's pushes and pulls point up or down. Flipping polarity (often labeled Ø and wrongly called "phase invert") turns the waveform upside down. It doesn't move anything in time.
- Snare bottom: it faces the opposite direction to the snare top, so when the drum is hit the heads move toward one mic and away from the other. Flip the bottom mic's polarity and the snare usually gets fuller.
- Kick in and kick out: same idea. Try flipping one and keep whichever sounds bigger.
- DI + amp mic: the mic is a little late compared with the DI. Flip polarity to test, then nudge the mic track earlier by a fraction of a millisecond, or use an alignment plugin.
Phase is about timing. Polarity is about direction. A polarity flip fixes opposite-facing mics; time alignment fixes mics at different distances.
Re-Amping
Re-amping means sending a recorded DI track back out of your interface into a real guitar amp, then miking the amp again. You get to choose the amp tone after the performance is captured, or try different amps and mic positions without asking the player to play it again.
The software version is even easier: put an amp simulator plugin on the DI track and change it any time.
Recording Keys & Synths
- Stereo outputs: most keyboards and synths have left and right outputs. Record them into two line inputs as a stereo track. Pads and pianos often sound much wider and more alive in stereo.
- Line level: keyboards put out line level, so plug into a line input (or use a DI box for long cables). Set gain so peaks land around
-12 dBFS. - Record MIDI as well: if the instrument has MIDI out, record its MIDI on a separate track at the same time. You can fix a wrong note and re-record the audio later (see MIDI).
- Acoustic piano: a pair of condensers inside the lid, over the hammers (about 20–30 cm above the strings), spaced to cover low and high strings.
- Record an electric guitar or bass through the Hi-Z input on your interface to a mono audio track, peaks around
-12 dBFS. - Add your DAW's amp simulator [Ableton: Amp + Cabinet; FL Studio: a free third-party amp sim plugin; Logic: Amp Designer or Bass Amp Designer] and try three different amp tones on the same performance.
- If you have two mics, record an acoustic guitar or a shaker in XY: capsules touching, angled 90°. Pan the tracks hard left and right.
- Now move them to a spaced pair about 1 m apart and record again.
- On the master, add a utility or imager plugin set to mono [Ableton: Utility, Mono; FL Studio: Fruity Stereo Shaper with a mono setting; Logic: Gain plugin, Mono]. Compare how each recording holds up in mono.
- Flip the polarity of one track [Ableton: Utility, Phase L/R; FL Studio: mixer track menu, Reverse polarity; Logic: Gain plugin, Phase Invert] and listen to how much the sound changes.
A good starting point for miking an acoustic guitar is the fret.
The 3:1 rule says mics should be at least times further from each other than from their sources.
The snare bottom mic usually needs its flipped.
The stereo technique that uses a cardioid and a figure-8 is called .
1. You point an SM57 at the dead center (dust cap) of a guitar speaker. What tone should you expect?
- Very dark and muffled
- Thin and roomy
- The brightest, most aggressive tone
- No difference from the edge
The center of the cone gives the most high end. Moving toward the edge sounds darker and warmer.
2. Which stereo technique is the most mono-compatible?
- A wide spaced pair of omnis
- Two mics on opposite sides of the room
- One mic panned hard left
- Mid-side
In M/S the two side signals cancel when summed, leaving the clean mid mic. XY is also very mono-safe.
3. Why does the snare bottom mic usually need a polarity flip?
- It faces the opposite direction to the top mic, so its waveform is upside down compared with the top
- It's further away from the drummer
- It uses a different type of mic
- To make it quieter
When the drum is hit, the head moves toward one mic and away from the other. Flipping one lines them back up.
4. What is re-amping?
- Turning an amp up louder
- Sending a recorded DI track back through a real amp and recording it again
- Replacing a guitar with a synth
- Using two amps at once while recording
Re-amping lets you choose or change the amp tone after the performance has been recorded.
5. Two mics pick up the same drum but sound thin and hollow when mixed together. What's the likely cause?
- Too much reverb
- The sample rate is too low
- Phase problems (comb filtering) from the different arrival times
- The drum is out of tune
The sound reaches the mics at different times, so some frequencies cancel. Move a mic, follow the 3:1 rule, or time-align the tracks.