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Show HN: I made a free app to calibrate your turntable by simply playing a song

grooved.okat.best

61–70 of 239 posts

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#61

Strongly recommend updating your website to lead with some variation of "This is an offline iPhone app to help you calibrate your turntable's speed, all you need to do is play your records and the app will show you the current RPM" — wayyyyyyy too many words and other nonsense before I could figure out this is what it did. Embed the demo video (the tweet you linked) too! Looks great and if I still used records I woul…

I thought the copy was fun and don't mind a good soapbox every once in a while, but yeah, wouldn't hurt to slip in a few words about what exactly the product does earlier on.

I'll definitely be trying this out on my decks before my next set :)

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#62

Strongly recommend updating your website to lead with some variation of "This is an offline iPhone app to help you calibrate your turntable's speed, all you need to do is play your records and the app will show you the current RPM" — wayyyyyyy too many words and other nonsense before I could figure out this is what it did. Embed the demo video (the tweet you linked) too! Looks great and if I still used records I woul…

I thought the copy was fun and don't mind a good soapbox every once in a while, but yeah, wouldn't hurt to slip in a few words about what exactly the product does earlier on. I'll definitely be trying this out on my decks before my next set :)

Updated my comment for clarification, agreed the extra copy is fun.

Also hi joe :^)

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#63
post #51

This is a neat idea. I don't know why it needs to be an app on a phone though. I guess you "know" a phone has a microphone and the setup is minimal and you have a api for everything? It being a phone app leads me to believe the 'no data collected' bit is temporary as all phone apps eventually gobble data to sell. I have an Android so I can't try this out, as its in 'private beta' on Android currently. Would love to s…

Probably a smart idea to be suspicious of new apps, though I will say I am someone who care deeply about privacy. You can take a look at my previous project Boop ( https://boop.okat.best/ ), which is open source and has been on the App Store for 6 years, yet I still don't have any analytics or data collection in it. I have no clue how many people use it beyond download figures I get from Apple.

I have considered making this app open source, and it may still happen in the future, but I do want to release the Android version first. I'm worried that somebody will see my code, repackage it with a new name, beat me with better SEO (which would be easy considering how dumb the copy is on my website) and sell it for profit before I have a chance to reach a wider audience. This is something that did happen with Boop, not a hypothetical.

The reality is that this app cannot collect anything valuable either way. It's a simple serving app that only uses your microphone for a couple of seconds at a time, and I assume most people will delete it once it serves its purpose. If I wanted to monetize it, the best way would be to add a "Pro" version with a subscription or to add ads, but I have no interest in doing either. This is a fun side project/portfolio piece, and I'd rather collect internet love distributing a ton of free copies, rather than sell a small fraction of that number of paid copies for $0.99 and have to deal with things like marketing, taxes, and customer support.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#64
post #53
post #47

Earlier quoted context omitted.

You can extract pitch information and compare it to a set of quantized reference pitches as an instrument tuning app does, sure. But you can also extract BPM info and compare that to a set of quantized reference BPMs that anyone would ever bother to use. And also, since you’re getting multiple pitches from multiple instruments in a time series, if you can isolate particular instruments, you can calculate the key the…

Are there really "standard" BPM? As far as I know, most music production is just "whatever tempo the band feels like playing." I haven't been in a recording studio, though, so maybe a use of a metronome is more common there?

I'm not in the music industry in any capacity myself, so take everything I say here with a grain of salt.

And more specifically, to address your question, I don't know enough about the recording part of music production to say whether most performers get a click-track played into their monitors or not. (I know that I've seen at least some performers using click-tracks for studio recording; but I'm not sure if that's only given if they ask for it, or if it's the studio pushing it on performer to make their jobs easier. I imagine click-tracks would always be used for multi-performer async studio recording — as otherwise you'd have performances that have conflicting BPM. But maybe not for single-performer pop/EDM songs, where it's just a vocalist laying down a track, and then everything else is done in software?)

The evidence I can cite, is from the outcome of the production process: I have a strong recollection from back in the late 2000s, of using some music library auto-tagging software that would, among other things, analyze the BPM of a song to populate the BPM ID3 field of MP3s. For at least the music I loaded into it, BPM did appear to be (mostly) quantized to nice, round numbers. (And it wasn't just the software being coarse-grained in its estimates; it did give weird numbers for unusually-produced songs.)

I do know that for any modern "produced" music (i.e. music not recorded as a live ensemble session), even if the performers did lay down their tracks at a weird BPM, the audio engineer is still going to be throwing their performances as separate tracks into a DAW. And one of the things you tell a DAW, when creating a project, is the BPM — which creates a grid of bars that tracks/samples want to snap onto. Even if you're not trimming or speed-adjusting performances so as to snap the ends of each track/sample to the DAW's grid, you're still likely snapping the beginning of each track/sample to the grid — you'd have to fight the DAW to not. Which means that, by default, if the song is "produced" enough — tracks cut up and slid around, reused, etc — then the output of this moving-and-snapping process will be a song that reads as the project's BPM.

Separately, I know that people learning to play an instrument for classical/orchestra music, often practice their instrument using a metronome (at least at the early levels.) Which perhaps gives at least some of those people the speed equivalent of perfect pitch — the ability to "lock into" certain BPMs; and to know if other performers are running fast/slow vs the "expected" BPM of the song.

I would assume that even for rock performers with no classical training, the early-level "textbook" practice for drummers and rhythm guitarists also involves playing with a metronome. It might be a lot more tenable to play a rock song at e.g. 117BPM, if everyone's just playing on the down-beat of the drums; but these performers still don't want to have a sudden, unintended shift in their BPM due to not being able to do a drum fill / complex chord change quickly enough; nor to start rushing as the song amps up, forcing everyone else into increasingly-stressful playing. In doing drills with a metronome to keep their BPM constant, these performers are likely implicitly learning to lock into certain specific BPMs as well.

My impression is that the one case where this probably isn't true, is in live jazz performance, and more specifically in live jazz improv "jam sessions." In those, the percussion (if any) isn't driving the performance, but rather is just another component of the harmony, following the (often wavering!) BPM of the lead performer.

(Is this why the classic meme of classically-trained performers not getting along with jazz artists? Because the jazz artists won't stay on beat, and this irritates some perfect-pitch-like "out of tune" feeling in the classical musician?)

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#65

You can get apps where you place your phone on the turn table and it directly measures the turntable speed using either gyroscope or compass https://play.google.com/store/apps/details?id=com.vinylrpm&h...

Here I was thinking it'd be smart to have the app use the camera to figure out how fast the middle label is spinning around but this seems way simpler now that you mention it.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#66
post #56

Earlier quoted context omitted.

Umm, no, scratches meet the needle once per revolution, regardless of the needle's position. So that would definitely be a possible method. But not all records have scratches, or they could be at an angle, which would give the wrong estimate. Also, actual sounds on the record could have scratch-like qualities.

>scratches meet the needle once per revolution, regardless of the needle's position I need to go away and think about that :D

The needle doesn't pass at a constant "ground speed" everywhere on the record. On the outside the needle "travels faster" and in theory you have more detail. Near the middle the needle travels over the record surface slower.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#67
post #29

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

> Are essentially all albums perfectly in tune with A 440 hZ? For example with classical music, I understand that 442 is also used, baroque is sometimes at 415, and 432 has been common as well? I don't know about pop but I can't help but wonder if some artists have intentionally chosen something other than 440 over the decades. No they are not all tuned to 440Hz. This is really evident if you play an instrument and w…

Every. Rolling. Stones. Album.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#68
All the turntables in my life as a kid had built-in calibration, in the form of four rows of repeating black/silver squares on the side of the wheel, a light flickering at the mains frequency, and a little dial to adjust the turning speed until the row of squares corresponding to your current combination of 50/60 hz DC and 33/45 RPM appeared to stop moving. It was a very clever trick.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#69
post #44

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

ShazamKit, from that fetch the BPM, BPM detection from the mic, compare ?

It works offline, though.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#70

I'm skeptical; you have no idea whether a random song from a record player is in tune or not, without a reference copy of that song from digital media. Is this zeroing in on traces of 60 cycle hum in the recording? Or else, won't it adjust an out-of-tune song to be in concert pitch? (Mind you, that would be extremely useful if you're playing along with the track and don't want to adjust your instrument, or cannot do…

60 cycle hum probably would not work, europe uses 50hz
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