If you really want a piano, a keyboard is a lousy substitute...but a piano is an equally lousy substitute for a versatile fun packed keyboard!
A piano usually sounds good, has weighted keys, weighs hundreds of pounds, is NOT easily moved, and except for changes in the surrounding atmosphere, usually has the same quality sound from one day to the next... unless it is out of tune.
A portable keyboard usually sounds good, has 'touch sensitive keys' that are often weighted like a real piano, weighs between 10 and 70 pounds, is obviously portable and runs on electricity. (Some of the smaller portable keyboards also run on batteries: I recommend rechargeable batteries if you go this route.)
Keyboards never go out of tune and have hundreds of voices and rhythm patterns built in. They can be hooked directly to a computer (via MIDI cables or audio jacks) to record and playback your own performances, and MIDI files can be played through any other MIDI compatible instruments.
When considering a portable keyboard, you need at minimum (1) a Sustain Pedal jack and (2) no less than 64 note Polyphony. (POLYPHONY refers to the number of tones that can be simultaneously played or 'caught' by the Sustain Pedal at one time. MORE polyphony is always BETTER!)
When you play the GRAND ARPEGGIOS found within Advanced PMMO, you'll sometimes be playing as many as 200+ tones at once (caught by the sustain pedal). Yet, if your keyboard has only 64 polyphony, only 64 tones will play. As each new tone is played, the oldest 'drops out' of the sound. What's more, if the piano voice you're using uses 2 slots of polyphony, you'll only hear a maximum of 32 tones at once, when playing a 64 polyphony instrument. (My performing keyboard has 256 polyphony.)
Even so, a 61 note Keyboard with a POLYPHONY Of 64 or 128 will sound quite good! Unfortunately, polyphony less than 64 is quite noticeable and should be avoided.
In most ways, portable keyboards share very similar basic features. They:
Better sound straight out of the box will cost more, yet any portable keyboard can be amplified through the speakers of a home stereo and yield a pretty good sound.
The physical feel of striking a key on some portable keyboards is very soft and light; more like playing keys on an organ than a piano, but the touch on higher quality keyboards often feels as good (or better) than a real acoustic piano.
As mentioned above, a keyboard is a lousy substitute for a piano, but a piano is an equally lousy substitute for a portable keyboard. If you absolutely need the sound and feel of a piano...GET A PIANO! But if you want to learn how to play piano and be portable, save bucks... PLUS have a fun variety of 'bells and whistles' for effects, GET A KEYBOARD! Better yet, get BOTH!
Briefly, the important features of a keyboard to consider are:
Some PMMO members have found excellent 'like new' portable keyboards with case, stand and bench, for less than $10.00 (U.S. Dollars)! Where? YARD SALES, GARAGE SALES, FLEA MARKETS, EBAY, etc. In addition, if you'll make it known to family and friends that you're looking for an instrument, you just might get one for free!
WHY free? Because almost 90% of people who own an instrument never learn to play it! Getting rid of a useless instrument is one less thing to dust; one less piece of clutter! Their pain can be your gain!