Parlour

Listen

The same twenty seconds, four ways: the music as your app plays it, and through Parlour on a mint, a played and a thrashed record. Press play and switch while it plays; every version is at the same loudness.

Frédéric Chopin, Waltz in A flat major, Op. 69 No. 1, played by Luke Faulkner. Recording from Musopen via the Internet Archive, Public Domain Mark 1.0. Through Parlour: the Mint, Played and Thrashed records, each with its own wow.

How it was made

Parlour takes the sound of your music app with a Core Audio process tap, the part of macOS that lets one app hear another's output once you allow System Audio Recording. The sound runs through a buffer of under half a second and out to your speakers. Nothing is written to disk and nothing leaves your Mac.

Every sound Parlour adds was measured from real records first. The reference set is the Boston Public Library's LP collection on the Internet Archive: library records from 1949 to 1968, transferred at 96 kHz on one Technics deck with an Audio-Technica cartridge. Five lead-ins, one run-out groove, four landings and one lift came from that set. That is enough to settle the shape and size of each sound, not to tune it to the decibel; every figure below is from the records we measured.

The surface. On those records the high-frequency surface noise sits 31 to 43 dB under the music. Parlour makes its surface as a record does: the noise is added at the disc and passes only through the playback curve, while the music, cut and played back through matching curves, comes out flat. That is why a record's hiss is soft and dark, not a bright fizz.

The clicks. The real lead-ins carry 58 to 146 clicks a second standing out from the floor, most of them tiny and a few very large: the count roughly halves with every 5 dB of size. Parlour's clicks follow the same curve (about 52 a second on the Played record, about 118 on Thrashed). On one run-out groove a flaw came round every 1.800 seconds, once a turn at 33⅓, as a cluster of 10 to 15 clicks; Parlour's defects come round once a turn too.

The needle. A real landing is two events: a low thump as the stylus touches down, then the groove catching it, usually 0.20 to 0.26 seconds later and now and then over a second later. In between, the stylus slides on the lead-in and the surface noise swells by about 13 dB in the mids: every one of six real landings caught the groove, and Parlour's do too. When the needle lifts, the hiss stops at once and a low thump rings down; one shape (17.4 Hz, 9.7 ms) fits all three real lifts we measured, from two decks.

Turning the record over, and the turn itself. The side break is timed and voiced from two continuous rips of real side changes, from the lift to the drop onto side two. One deck has a thump from its cue lever and the other none, so Parlour has one on about half the flips. Where it could be measured, the hiss swelled 1.3 to 2.0 dB once per revolution; Parlour's Played record swells 1.5 dB and its Thrashed one 2.

Three conditions, measured, not invented. Mint, Played and Thrashed are three records, not three positions of a crackle slider. Each sets its surface, clicks and wow together, and at start-up Parlour measures its own noise through the whole chain and trims it to that condition's target.

Wow. A record's hole is never quite in its centre, so the speed rises and falls once a turn, more toward the inner groove. Parlour reads its buffer with a fractional read head that follows that swing: on the Played record about 0.1% at the outer groove, about 0.22% twenty minutes in. It keeps the treble: with wow on and off, every third-octave from 10 to 20 kHz came out within 0.012 dB.

The transport. On play, Parlour pauses the music app, drops the needle, plays the lead-in, then lets the app play, so the first note follows the landing and none of it is missed. Between songs it pauses the app as the new track arrives, plays out the old one's end, runs the groove, and plays again. The gap comes out between about 1.8 and 2.5 seconds, depending on how quickly the app starts the next track, much as the spirals between bands differ from record to record. Of the quarter second Spotify fades out when it is paused, 17 ms is never heard; the rest is put back as it was.

What it does not do. Parlour does not make your music louder or squeeze it; move the app's volume slider and the surface follows, as through a real amplifier. It adds no "warmth" curve of its own: the music gets what a record's playback chain does to it (the bass gathered toward the middle, the cartridge's gentle top-end roll-off, a little dulling toward the inner groove), and a limiter just under full scale is there only for a hard landing. With the needle up it is silent, and the bypass hands back your music bit for bit.

Listen closely

• The lead-in: the needle lands, the surface plays for a moment, and only then does the first note come.
• The surface under the quiet bars, soft and dark rather than a bright fizz.
• The hiss rising and falling a little, once every turn of the record.
• The groove catching the needle, a short tick a quarter of a second after the thump of the landing.
• The music's own loudness, which is the same in every version.