Nightcore, daycore, chopped and screwed.
What the words actually mean.

The words, defined

Alphabetical. Where Y2K Player has a preset of the same name, its real numbers are given.

BPM

Beats per minute: how many times the main pulse falls in one minute. It measures tempo and nothing else — not key, not loudness, not genre. It is ambiguous by nature, because the same music supports counting the pulse at half or at double speed, which is why two apps can analyse one file and disagree by a factor of two. Y2K Player estimates across a 58 to 215 BPM range, reports nothing when there is no steady pulse, and shows what you are hearing rather than what the file was: a 120 BPM song played at 125% reads 150 BPM.

Chopped and screwed

A Houston technique from the early 1990s, associated with DJ Screw. Two operations, not one. Screwed is the whole record slowed down, the pitch dropping with it. Chopped is short passages caught and played again by hand — a stutter, a rewind, a bar doubled — on a second copy of the same record. Most of what circulates under the full name is only the screwed half. The Chopped preset does both: 0.72× with the pitch linked, and a chop locked to the song’s detected beat grid, capturing every eight beats in sixteenth-note slices.

Daycore

The inverse of nightcore: tempo and pitch pulled down together, so the song loses speed and drops in key at once. Also called anti-nightcore, it usually sits between 0.70× and 0.80×. What separates it from slowed and reverb is that daycore is about the changed voice, and needs no room behind it. There is no daycore preset in Y2K Player and none is needed — it is the tempo slider with the pitch link on, and at 0.75× the song lands five semitones down.

Lo-fi

Short for low fidelity: sound deliberately degraded — a ceiling on the bandwidth so the top end disappears, the swirl of low-bitrate encoding, added grit. It is a quality, not a tempo. That is the usual confusion: lo-fi hip hop, the playlist genre, is slow and degraded, so someone asking for a lo-fi version generally wants both. The Lo-Fi preset does both: 0.92×, with the Low Quality effect at an Age of 42 out of 100.

Nightcore

Speeding a song up so that its pitch rises with it. That link is the defining property, and the difference between nightcore and an ordinary sped up edit, where the pitch is usually held in place. It began with fans of eurodance and trance playing records faster, and takes its name from the duo the practice grew around. The usual range is 1.25× to 1.35×. The Nightcore preset sets 1.35× with the link on, which puts the pitch 5.2 semitones up.

Phonk

A genre, not an operation — the one word here that no setting will produce. It grew out of 1990s Memphis rap — cowbell, distorted 808s, chopped and pitched vocal samples, tape hiss — revived online from the late 2010s, with drift phonk as its faster, harder-distorted branch. Because phonk is a set of samples and arrangement choices, a song can be pushed closer to how phonk records sound but not converted into phonk. Y2K Player has no phonk preset; what overlaps is the Distorted preset — 0.94× with Drive at 46 — and the chop.

Semitone

The smallest interval in standard Western tuning: twelve to an octave, a frequency ratio of the twelfth root of two, about 1.0595. Pitch is measured in semitones rather than hertz because the ear hears ratios, not differences. Speed and pitch are one quantity when a file is read faster: the shift is twelve times the base-two logarithm of the speed. Y2K Player’s pitch control runs −12 to +12, and with the link on, 200% reads +12, 150% about +7, 125% reads +3.9, and 50% reads −12.

Slowed and reverb

A song played slower than it was recorded, with reverb added so it sounds like it is happening in a large room. The pitch nearly always comes down with the tempo — the darkness people describe is the pitch, not the speed. The usual range is 0.80× to 0.90×, and the second half of the name is not decoration — a slowed song with no room around it is just a slow song. The preset sets 0.85× with the link on and reverb at a Mix of 34%, which lands the pitch 2.8 semitones down.

Time-stretch

Changing how long audio lasts without changing its pitch. It is not what happens when a record plays faster — that is resampling, which moves speed and pitch together as one. It cuts the signal into short overlapping windows and re-spaces them, so each window keeps its pitch while the duration changes; the cost is smeared transients and a metallic quality under heavy stretching. Y2K Player runs a resampler and a stretcher in a row: link on, the resampler carries everything; link off, the stretcher does, and the key survives.

Wet/dry

The balance between the processed signal and the untouched one. Fully dry is the original with the effect inaudible; fully wet is the effect alone. Reverb in particular falls apart near the top: past halfway the dry song is quieter than the room it sits in. In Y2K Player the control is called Mix, and reverb’s stops at 50% for exactly that reason.