Tension glide string

How it works

• Single string; a motor varies tension for continuous pitch only (swoops, microtonal drift, vibrato).
• Sustained by an EBow-style driver or rosin wheel rather than plucked.
• Range is about a fourth to a fifth; an octave needs 4x tension.

Build notes

• Pull the tailpiece with a lead screw rather than motorizing a tuning peg (pegs are slow).
• Avoid friction at nut and bridge. Closed loop: load cell for tension, pitch detection to recalibrate.

Risks

• Strings are consumables under cyclic tension.

References

• Pedal steel changer and timpani pedal. Precedents for changing pitch by tension.
• THX “Deep Note.” A cluster of detuned voices gliding into one chord. A model for tension-tuned strings gliding into tune.
• EBow. Electromagnetic string sustainer.