It listens to what you actually play, not what a lesson plan assumes you need, and deals you the note you keep getting wrong ten times more often than the one you’ve already got.
MidiSlayer is a desktop app that listens to a MIDI keyboard over USB and grades every note you play against real notation, in real time, across nine training modes, three arcade games and a 69-piece score library running from Twinkle, Twinkle to the complete Goldberg Variations. It ships in Early Access for macOS, Windows and Linux, from Monoglyph Ltd, a small UK company that also makes rhythm-notation audio plugins.
Sight-reading is where adult piano learners tend to stall: you can play a piece from memory long before you can read one cold, and the trainers built for it usually drill notes in a random or fixed order, so you spend as much time on notes you already know as on the ones actually tripping you up.
MidiSlayer’s answer is a weighted deck. In its own words, a note you’ve never played is dealt at ×10 and “dealt first,” one you recently missed comes back at ×4, “three days overdue, dealt often,” and one you’ve nailed drops to ×0.5, “still dealt, now and then.” The same deck runs under chords, intervals, scales, key signatures and real pieces too; one piece per shelf, four in all, is free to play, and the rest of the 69 unlock with the $49.99 one-time purchase, which also opens MusicXML import, so a teacher’s arrangement or an exam piece becomes sight-readable the moment you drop the file in.
The newest release, out the day before this review, gave the improvising mode, “The Session,” a live band: real drums and a double bass that count you in, hold a straight, swing, ballad or bossa groove, and listen to how hard you hit each key. Free players get one loop of it; buying unlocks the rest, plus Blitz and Cascade, the two named arcade games (Blitz is free in full, Cascade gives free players one run a day as the Daily Challenge). Every session logs to an on-device dashboard — sessions, notes played, hours practiced, a map of your slowest notes — under a line the FAQ states outright: “No ads. No profiles. No peeking.”
The catches are the ones Early Access implies. It wants a real USB MIDI keyboard, from a $25 controller to a digital grand — the on-screen keyboard is only there to try the app before buying one. A chunk of the value sits behind the paywall: the full library, exam mode’s per-skill ranks, MusicXML import, and activation on a second machine. The Show HN launch drew three points and no comments yet, so there’s no outside pressure-test beyond what the site’s own pricing and changelog pages show.