Casio Privia PX-S1100 Review: How It Compares With Yamaha's P-125

The Casio PX-S1100 uses Casio's Smart Scaled Hammer Action Keyboard, which Casio says reproduces individual hammer behavior for each of its 88 textured keys, with five touch-sensitivity levels. In owner reports and published reviews it's usually described as lighter and quicker than Yamaha's entry-level actions, which suits pop, jazz and players coming from synths; some classical-track players find it too light for building control in slow passages.

The Yamaha P-125 uses Graded Hammer Standard (GHS), Yamaha's entry-level graded action, also used on the P-45. GHS is usually described as heavier and more traditional than Smart Scaled, closer to an acoustic upright, with a more deliberate keystroke. Many classical-track teachers like that weight for building finger control; the trade-off is that some players find it less responsive for fast lines.

The PX-S1100 runs Casio's Multi-dimensional Morphing AiR Sound Source, derived from the company's higher Privia models. Reviewers generally describe AiR as bright and articulate, with a forward upper register that suits modern pop and jazz playing and layering with backing tracks. The trade-off: some classical-track players describe it as "too clean" or lacking the warmth they want for romantic-era repertoire.

The P-125 runs Yamaha's Pure CF Sound Engine, derived from the CFIIIS concert grand. Pure CF is usually described as warmer, with a fuller bass and longer sustain — the classic acoustic-grand character many teachers prefer for serious practice. The P-125 also has more voices: 24 vs the PX-S1100's 18, with wider electric piano and organ variety. For classical or jazz comping, Pure CF is the more traditionally piano-like sound.

The PX-S1100 is exceptionally slim for an 88-key hammer-action piano. At 9.1 inches deep, 4.0 inches tall and 24.7 lb, it is 2.5 inches shallower, 2.5 inches lower and 1.3 lb lighter than the P-125. Its touch-sensor control panel supports the streamlined design, and six AA batteries allow roughly four hours of untethered use. That combination remains a meaningful advantage for apartments, lessons, travel, and modern home setups.

The P-125 uses a more traditional slab design: 11.6 inches deep, 6.5 inches tall, 26.0 lb. It's still portable — the weight gap is only 1.3 lb — but it occupies meaningfully more shelf space, sits taller on a stand, and looks more conventional. Yamaha uses physical buttons along the top of the chassis, which some players prefer for direct access vs the PX-S1100's touch surface. There's no battery option on the P-125; you need an AC outlet at all times.

The PX-S1100 supports Bluetooth audio and MIDI through the included WU-BT10 adapter. You can play music from your phone through its speakers and use apps wirelessly; the adapter is included, but the Bluetooth hardware isn't built into the piano itself. Casio Music Space handles voice selection, recording and lesson features. When the adapter isn't fitted, the USB-A port takes a USB drive for recording and playing back MIDI songs and WAV audio.

The P-125 has no Bluetooth in Yamaha's specifications. Where it wins is the app ecosystem: Smart Pianist is generally regarded as the more polished app, with sheet music display, voice selection and a cleaner interface than Music Space, and it works over a USB cable out of the box. Both pianos have a two-track song recorder for self-review during practice.