You can freely build on How Laurens Hammond Invented the Electric Organ

What this patent covers

The patent describes a system for generating musical tones using rotating electromagnetic tone wheels. As these metallic wheels spin near electromagnetic pickups, they create alternating currents that correspond to specific musical frequencies. These signals are then amplified and sent to a speaker to produce sound, effectively replacing the heavy pipes and air-driven bellows of traditional organs with compact electronic components.

What is now free to use

All 0 claims of US 1956350 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover digital synthesis or software-based sound generation.

• Does not cover modern MIDI-based keyboard controllers.

• Does not cover instruments that rely on vibrating strings or reeds.

Who is building on this today

The Hammond Organ Company established a legacy that modern digital keyboard manufacturers like Nord, Roland, and Yamaha continue to emulate through high-fidelity digital modeling of these original electromagnetic circuits.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 1956350. Electrical musical instrument. Granted 1934, expired 1954. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.