Hammond B-3 — Vol 03: Controls & Operation

This volume covers the player-facing control surface of the Hammond B-3: the drawbars, the preset keys, Harmonic Percussion, the scanner-based vibrato/chorus, the expression pedal, and the Start/Run powering-up ritual. The tone-generation theory behind these controls — the tonewheel generator, the 96 wheels (91 active), the nine key contacts per note, and the footage relationships — is established in Vol 02 §2.x and is referenced here rather than repeated. The Leslie 122 is Vol 04; the pedalboard and Trek II are Vol 05.

Note: Throughout this volume, drawbar registrations are written in the conventional nine-digit form grouped as 00 0000 000 (sub/quint — white-fundamental block — mutations), read left to right as the physical bar order 16′ 5⅓′ 8′ 4′ 2⅔′ 2′ 1⅗′ 1⅓′ 1′.

The drawbars

Each manual carries two sets of nine drawbars (a left set and a right set), and there are two further drawbars for the pedals — so the full bank is eighteen upper, eighteen lower, and two pedal bars (38 in all) (Hammond B-3/C-3 Service Manual; hammondwiki.org). The two sets per manual let the player park two contrasting registrations and switch between them with the preset keys (below). Each bar is a sliding harmonic control with nine detented loudness steps numbered 0 (off, fully in) through 8 (loudest, fully out); pulling a bar out adds more of that harmonic to the mix. The footages are pipe-organ nomenclature: the number is the speaking length of the organ pipe that would sound that pitch, so 16′ is an octave below unison and 1′ is three octaves above it (Vol 02 §2.x).

The bars are colour-coded by harmonic function. The white bars carry the fundamental (8′) and its octave members (4′, 2′, 1′). The two brown bars are the sub-octave 16′ and the sub-third quint 5⅓′. The black bars are the mutation/upper-harmonic ranks — the dissonant or “tinted” partials (2⅔′, 1⅗′, 1⅓′) that a player blends in sparingly for colour (Hammond B-3 Owner’s Playing Manual; hammondtoday.com).

#	Footage	Colour	Pitch relative to key	Harmonic role
1	16′	Brown	One octave below unison	Sub-octave (sub-fundamental body)
2	5⅓′	Brown	A fifth above unison	Sub-third / quint (3rd harmonic of 16′)
3	8′	White	Unison (the played pitch)	Fundamental
4	4′	White	One octave above	2nd harmonic (octave)
5	2⅔′	Black	An octave + a fifth above	3rd harmonic (nazard/quint mutation)
6	2′	White	Two octaves above	4th harmonic (super-octave)
7	1⅗′	Black	Two octaves + a major third above	5th harmonic (tierce mutation)
8	1⅓′	Black	Two octaves + a fifth above	6th harmonic (larigot mutation)
9	1′	White	Three octaves above	8th harmonic (octave)

Tip: The standard left-to-right physical layout is 16′ 5⅓′ 8′ 4′ 2⅔′ 2′ 1⅗′ 1⅓′ 1′ — note the 5⅓′ quint sits to the left of the 8′ fundamental even though it is a higher pitch, a layout quirk inherited from the original 1930s tonal scheme.

Preset keys

To the left of each manual sits an octave of reverse-colour preset keys (the naturals appear black, the sharps appear white) that recall complete drawbar registrations without touching the bars. The far-left reverse key, C, is the cancel key — it has no contacts and silences that manual (no registration, no sound). The two right-most keys, A♯ (B♭) and B, are the adjustable presets: each brings one of the manual’s two live drawbar sets into play — A♯ the left set, B the right set — so whatever the player has dialled into a set sounds only when its key is engaged. The keys between them (C♯, D … A) call up factory-wired internal registrations soldered to binding posts inside the organ (Hammond B-3/C-3 Service Manual; hammondwiki.org PresetPanel).

The table below gives the standard factory upper-manual wiring for the nine documented preset keys (hammondwiki.org StandardPresets). The lower manual carries its own, different factory set (e.g. Cello, Open Diapason, Full Great).

Reverse key	Function / name	Drawbar registration
C	Cancel — manual silent (no contacts)	— (no sound)
C♯	Stopped Flute	00 5320 000
D	Dulciana	00 4432 000
D♯	French Horn	00 8740 000
E	Salicional	00 4544 222
F	Flutes 8′ & 4′	00 5403 000
F♯	Oboe Horn	00 4675 300
G	Swell Diapason	00 5644 320
G♯	Trumpet	00 6876 540
A	Full Swell	32 7645 222
A♯ (B♭)	Adjust — left drawbar set	whatever is set on the left bars
B	Adjust — right drawbar set (also the percussion source)	whatever is set on the right bars

Note: The two adjustable drawbar sets per manual are reached by the A♯ (B♭) and B preset keys (the left and right sets respectively). In the classic playing technique a contrasting registration is parked on the inactive set so the player can flip between two live sounds mid-phrase with a single preset key. The far-left C key is the cancel (silent) — it has no contacts and recalls no registration. The percussion controls below operate only when the upper manual is played from the B (right-set) adjust preset.

Harmonic Percussion

Harmonic Percussion is a B-3/C-3 feature (not present on earlier models) that adds a decaying overtone “ping” to the attack of each note, evoking a marimba/harp/chime transient before the sustained drawbar tone settles in. It is generated on the upper manual only, and only when that manual is played from the B (adjust) preset (Hammond organ documentation; hammondwiki.org).

Four switches govern it:

• Harmonic selector — Second / Third. Second tunes the percussive overtone to the 2nd harmonic (one octave above the played note); Third tunes it to the 3rd harmonic (one octave plus a fifth above).
• Percussion volume — Soft / Normal. Normal is the louder, more pronounced ping.
• Percussion decay — Fast / Slow. Fast gives a short, sharp click; Slow lets the overtone ring longer before fading.

Two interactions are essential to the sound and define its character:

1. The 1′ drawbar is borrowed. When percussion is switched ON, the upper-manual 1′ drawbar is cut from the sustained tone — its tonewheel tap is re-purposed to feed the percussion trigger. The 1′ bar therefore goes silent in the drawbar mix whenever percussion is engaged (Hammond organ documentation).
2. Normal drops the overall level. Selecting Normal percussion volume produces a slight reduction in the manual’s sustained drawbar level, a side-effect of the way the percussion volume is gained against the main signal.

Warn: Harmonic Percussion is single-trigger and therefore deliberately non-legato. The percussion envelope re-arms only after all keys on the manual are released; during a legato line the ping sounds on the first note/chord only and stays silent under the slurred notes that follow. Lifting fully between notes restores the attack on each — this is why percussive B-3 lines are played with crisp, detached articulation.

Decay-time behaviour, stated qualitatively: Fast fades in a fraction of a second — on the order of ~0.2 s (est.) — while Slow rings noticeably longer, on the order of ~1 s (est.); precise figures drift with component age and are flagged as estimates rather than asserted from a single clone manual.

Vibrato & chorus (the scanner)

The B-3 vibrato and chorus are produced by an electromechanical scanner rather than by any electronic oscillator. The signal is fed through a multi-tap LC delay line (a ladder of inductor/capacitor all-pass sections), so each successive tap presents the same signal with a little more phase delay. A motor-driven rotary capacitor “scanner” — effectively a single-pole, sixteen-throw air-dielectric switch on the run-motor shaft — sweeps along those taps and back, continuously picking off progressively delayed (hence pitch-shifted) versions of the signal. Sweeping toward longer delay drops the pitch slightly; sweeping back raises it; the cyclic result is vibrato (Hammond B-3/C-3 Service Manual; hammondwiki.org Vibrato; modularsynthesis.com).

The scanner runs off the synchronous run motor at roughly 412 rpm, about 7 Hz vibrato rate (~6.9 Hz (est.) in practice) (hammondwiki.org Vibrato). The six selector positions split into two families:

• V1 / V2 / V3 — pure vibrato. Only the scanned (phase-shifted) signal reaches the output. The number sets depth: V1 scans about a third of the delay line, V2 about half, V3 the whole line — so V1 is shallow and V3 is wide.
• C1 / C2 / C3 — chorus. The scanned signal is mixed back with the dry, un-shifted signal. The fixed dry tone beating against the swept tone yields the shimmering Hammond chorus; C1/C2/C3 again widen the scan from shallow to full.

Upper and lower manuals have independent vibrato on/off switches, so the chorale of one manual can be wet while the other stays dry; the V/C selector itself is shared.

progressively delayed taps →

Rotary capacitor scanner (16-throw) sweeps taps up & back — ~412 rpm ≈ 7 Hz scanned (wet) + Out to amp

VIBRATO (V1–V3): wet only — depth = how much of the line is scanned. CHORUS (C1–C3): wet + dry mixed — fixed tone beats against swept tone.

The mechanism is detailed mechanically in Vol 02 §2.x (scanner construction and its place on the run-motor shaft); this volume treats it strictly as a control. The vibrato/chorus effect is upstream of the Leslie (Vol 04), so a player can stack scanner chorus and Leslie rotation independently.

Expression pedal

The B-3’s expression pedal is a swell/volume control acting on the whole instrument’s signal after the preamplifier — not a per-manual control and not a tone control. It is wired as a variable shunt (a multi-tap potentiometer arrangement) that attenuates the combined output level, so heel-down is soft and toe-down is loud across both manuals and the pedals together (Hammond B-3/C-3 Service Manual).

The taper is roughly logarithmic, matching the ear’s perception of loudness so that pedal travel feels even rather than bunched. Because the swell sits after the preamp and before the power stage, it controls dynamics without changing the harmonic balance set on the drawbars.

Tip: Since the pedal scales the entire instrument, expressive swells affect upper manual, lower manual, and pedal tone simultaneously — a deliberate sustain-and-swell technique, distinct from balancing manuals against each other (which is done with the drawbars and presets).

Start/Run & powering up

The tonewheel generator is turned by an AC motor that must be brought up to synchronous speed before it will hold pitch. Powering up is therefore a two-switch ritual using the Start and Run switches (Hammond B-3/C-3 Service Manual):

1. Hold the Start switch (the spring-loaded one). This energises a separate, self-starting run-up motor that spins the generator assembly up from rest. Hold it for roughly ~8 s until the generator is up to speed.
2. With Start still held, throw the Run switch ON. This brings power to the synchronous motor, which locks the generator to the AC line frequency and holds pitch.
3. Release Start. The synchronous motor now carries the generator on its own; the run-up motor de-energises.

To shut down, the Run switch is simply turned OFF.

Note: The ~8 s hold is the conventional figure; the exact spin-up interval varies with line voltage and a given machine’s bearing condition, so it is given as an approximate ritual rather than a hard spec. The pitch stability of the whole instrument depends on the synchronous motor staying locked to the mains frequency (Vol 02 §2.x).

Driving it: a first registration

A worked example ties the controls together. The classic jazz starting point on the upper manual is the registration written 88 8000 000 — the 16′, 5⅓′, and 8′ bars pulled fully out (loudness 8) and everything above 8′ pushed in. This yields a fat, fundamental-heavy sound with the quint adding body, and is the bedrock “drawbar one” voicing from which countless gospel and jazz settings depart.

To bring it up on the instrument:

1. Choose the manual and preset. Set the upper-manual bars to 88 8000 000 and play from the B (adjust) preset so the live drawbars sound. (Cancel — B♭ — would leave the manual silent.)
2. Add the attack. Switch Harmonic Percussion ON — Third harmonic, Soft volume, Fast decay is a common first choice. Remember that engaging percussion cuts the 1′ drawbar (already at 0 here, so no audible loss) and that Normal volume would dip the sustained level slightly; the single-trigger behaviour means the ping returns only when keys are fully released.
3. Choose the modulation. Select C3 for a wide chorus shimmer, or a V position for pure vibrato; switch the upper-manual vibrato ON and leave the lower manual dry if a contrast is wanted.
4. Set dynamics with the foot. The expression pedal scales the whole result; ride it for swells.
5. Add the cabinet. Route to the Leslie 122 and use its speed control for the final voice (Vol 04 §4.x).

Tip: Parking a contrasting registration on the second (inactive) drawbar set lets the player flip between, say, 88 8000 000 and a bright 00 8888 000 with a single preset-key stab — the core of the live B-3 “two-sound” technique.

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Sources consulted: Hammond B-3/C-3 Service Manual; Hammond B-3 Owner’s Playing Manual; hammondwiki.org (PresetPanel, StandardPresets, Vibrato); Mark Vail, The Hammond Organ: Beauty in the B; modularsynthesis.com (vibrato scanner); hammondtoday.com. Values marked “(est.)” are approximate and flagged where a single authoritative figure could not be confirmed.