Are the keys really weighted?

Yes. The Harmony 61 Pro has full-size weighted keys with user-adjustable touch response, which is unusual at this level. The action is heavier than a synth-style keybed, so it suits piano-style playing more than fast organ lines.

Does it work as a MIDI controller?

Yes. It connects over USB-MIDI to a computer or tablet and can send note and controller data. There are no drum pads or modulation wheel, so it is a basic controller rather than a full studio one.

What is included in the box?

You get the keyboard, a sustain pedal and a power supply. A music rest and manual are also included; a stand and headphones are not.

Can I use headphones and an amp at the same time?

Yes. There is a 1/8-inch headphone jack and a stereo 1/4-inch output, so you can run to an amp or PA while listening privately. The built-in speakers cut out when headphones are plugged in.

How many notes can it play at once?

Polyphony is 64 notes, enough for layered sounds and sustained chords without dropouts. That is more than most budget keyboards offer.

Is it good for a beginner?

Yes. Full-size weighted keys, 580 sounds and an included pedal make it a strong first keyboard. The heavy action and menu-driven effects may frustrate players who want fast synth sounds.