Both harmonicas and bagpipes produce sound by passing air over one or multiple reeds (tuned to resonate at specific fundamental frequencies), inducing oscillations in the reeds, which modulate the air flow. Bagpipes use pipes to amplify the sound, and harmonicas use the cavity between the reed plate and the body, and often the player’s hand.
A digital keyboard that doesn’t produce sound is just a fancy human interface device.
This definition wouldn’t apply to harmonicas nor digital keyboards, nor bagpipes arguably.
Both harmonicas and bagpipes produce sound by passing air over one or multiple reeds (tuned to resonate at specific fundamental frequencies), inducing oscillations in the reeds, which modulate the air flow. Bagpipes use pipes to amplify the sound, and harmonicas use the cavity between the reed plate and the body, and often the player’s hand.
A digital keyboard that doesn’t produce sound is just a fancy human interface device.