The musical instrument known as the "vibraphone" was first marketed by the Leedy Manufacturing Company in the United States in 1921. However, this instrument differed in significant details from the instrument now called the vibraphone. The vibraharp (Deagan) or vibraphone (Leedy) evolved in differing designs under the creative influence of two inventive and prolific German instrument designers employed by competing percussion instrument manufacturers.

In 1916, Herman Winterhoff of the Leedy Manufacturing Company in Indianapolis experimented with a variety of motor-mechanical arrangements in his search for a vox humana or tremolo effect from the bars of a three-octave F-F steel marimba, a novelty vaudeville instrument with thin, steel tone bars mounted to the keybed on tapered felt strips. He succeeded in 1922 by mounting a motor on the frame at the narrow end beneath the bars to drive dual shafts fitted with metal discs centered in the tops of each resonator tube. As the discs (pulsators) revolved in the resonator columns under sounding bars, a tonal phase shift was created resembling a vibrato.

The Leedy vibraphone achieved a degree of popularity after it was used in the novelty recordings of "Aloha 'Oe" and "Gypsy Love Song" by vaudeville performer Louis Frank Chiha ("Signor Frisco"). This popularity led J. C. Deagan, Inc. in 1927 to ask its Chief Engineer, Henry J. Schluter, to develop a similar instrument. Schluter's design introduced several significant improvements: making the bars from aluminum instead of steel for a more "mellow" basic tone; harmonic tuning which adjustmented the dimensions and tuning of the bars to eliminate the dissonant harmonics present in the Leedy design; and the introduction of a damper bar controlled by a foot pedal, enabling it to be played with more expression.

The design drew on the earlier Deagan aluminum bar song bells and he large pipe organ vibrato-harps, hence the chosen name for the instrument, "vibraharp". J. C. Deagan is reported to have been somewhat dubious about the sales potential of the mellow sounding instrument in an age of crips and robust mallet instrument sounds. Nevertheless, he approved the new instrument and it ws put into productoin as the Model 145, the first musical instrument of complete American conception and the predecessor of all vibraphone models yet to come.

The new Deagan vibraharp was first heard on a radio broadcast over station WLS Chicago in the fall of 1927 when ace drummer Roy Knapp and the Chicago Little Symphony played a solo arrangement of Mother Machree with string accompaniment. By the time the first promotional flyer on the vibraharp was completed in 1928, a number of percussionists were already featuring "the new sensation in tone" (as it was advertised) in their musical groups. This was at a time when recording, broadcast and dance bands were seeking distinctive sounds in their arrangements and instrumentation. The impact of the vibraharp on the musical world was commencing.