Sound Instruments · free for iPhone and iPad

Four ways to see sound.

Play a note, whistle, talk or turn up a song, and watch it from four sides: its frequencies, its waveform, its octave bands and its history. Live, on your phone, from the microphone. Free to download.

Coming soon to the App Store, free What's free, what's Pro
Spectrum analyzer

Fourier. See every frequency.

A single note is never just one frequency. Fourier draws the whole stack, one sharp peak per tone: the fundamental, every harmonic above it, and how a filter or a change of waveform reshapes them.

  • Drag across the spectrum to read frequency, level and musical note.
  • Pinch to zoom frequency, pinch up and down to set the level, and pan with two fingers.
  • Hold peaks, choose an FFT window up to 8,192 samples, and play pink noise. Pro
  • Save a spectrum as a reference over the live one, and export CSV. Pro
Range
20 Hz – 20 kHz
Window
Up to 8,192 points
Readout
Hz · dBFS · note
Oscilloscope

oScope. Watch sound move.

Live mode scrolls the last two seconds of sound across the screen. Trigger mode catches a repeating wave and holds it still, so a sine, a square and a sawtooth each show their true shape.

  • Pinch sideways from 2 seconds down to 0.2 milliseconds, and up and down for amplitude.
  • Go full screen, freeze a moment and look closely.
  • Trigger: drag the level, pick a rising or falling edge, and hold a steady sweep. Pro
  • Average 4, 16 or 64 sweeps to pull a signal out of noise; save and export. Pro
Time
0.2 ms – 2 s
Modes
Live · Trigger
Averaging
4 · 16 · 64
Real-time analyzer

Octave. Octave bands, done right.

The bands sound engineers use to tune rooms, cars and PA systems, built to the ANSI and IEC filter standards. Pink noise reads flat, the way it should. Find the bass, then average over exactly the time you hold your finger down.

  • Whole, third, sixth and twelfth-octave bands, all free.
  • Tap a band to read its level and name; step through bands with the arrows.
  • Hold to record an Leq average and keep it on screen; Slow weighting. Pro
  • Pink noise, saved reference traces to compare EQ changes, CSV export. Pro
Bands
1 · 1/3 · 1/6 · 1/12 oct
Filters
ANSI S1.11 / IEC 61260-1
Weighting
Fast · Slow · Leq
Live spectrogram · new

Soundscape. See sound over time.

Pitch runs up the screen, time runs across it, loudness becomes color. A whistle draws a line, a voice draws stripes, and a song fills the screen layer by layer. In the film, the music spells words, and Soundscape draws them.

  • Touch any line to read its frequency, level and note.
  • Pinch sideways to zoom in time, up and down to zoom frequency, and drag to scroll.
  • Record up to ten minutes and replay it with its spectrogram. Pro
  • Compare two snapshots side by side; more color maps, a decibel scale and CSV export. Pro
Axis
Log frequency
Color
Linear or dB scale
Readout
Hz · dBFS · note
What they're for

Bring them to the job.

Each instrument does one thing well. Here is how people put them to work.

Car audio · Octave

Tune a car stereo with pink noise.

  1. Play Octave's pink noise through the car's speakers.
  2. Set 1/3 octave, sit in the driver's seat and hold to average while you move the phone around your head.
  3. Save it as a reference, change the DSP's EQ, and measure again over the saved trace.
Live and church sound · Fourier, Octave

Find the feedback before the congregation does.

When a monitor starts to ring, Fourier shows a single tall peak with its exact frequency and note. Octave tells you which third-octave band to pull down on the graphic EQ. Pink noise and an average show the room's response at the mix position.

Synths and music · Fourier, oScope

See why a square wave sounds hollow.

oScope shows the shape; Fourier shows that a square wave has only odd harmonics while a sawtooth has all of them. Sweep a filter and watch the harmonics fall away. Whistle and read your pitch as a note.

Teaching · all four, free

A physics lab in every pocket.

Everything a class needs is free: the spectrum, the waveform, the bands, the spectrogram, and touch readouts in hertz and notes. A built-in demo signal works without the microphone, so a whole room can follow along.

Free and Pro

Free to watch. Pro to measure.

Every app is free: the live instrument and its readouts, with no time limit. Pro is a one-time purchase per app that gives you full control and the tools of a measurement session: hold, compare, generate and keep.

Fourierspectrum analyzer

Free

  • Live spectrum, log or linear
  • Touch readout: Hz, level, note
  • Pinch zoom, freeze, test tone

Pro

  • Peak hold and decay
  • FFT window 256 to 8,192
  • Snapshots as references
  • Pink noise
  • CSV export
$9.99 once for Pro

oScopeoscilloscope

Free

  • Live waveform, 0.2 ms to 2 s
  • Pinch zoom, full screen
  • Freeze, test tone

Pro

  • Trigger with level and edge
  • Average 4, 16 or 64 sweeps
  • Snapshots as references
  • CSV export
$4.99 once for Pro

Octavereal-time analyzer

Free

  • ANSI / IEC bands, 1 to 1/12 octave
  • Fast weighting, RMS dBFS
  • Tap a band to read it

Pro

  • Leq averaging
  • Slow, Quick and Leq weighting
  • Peak hold, floor and ceiling
  • Snapshots and pink noise
  • CSV export
$14.99 once for Pro

Soundscapespectrogram

Free

  • Live spectrogram
  • Touch readout: Hz, level, note
  • Two color maps, short history

Pro

  • Record and replay, up to 10 min
  • Compare snapshots side by side
  • Long history, more color maps
  • Decibel scale, FFT window
  • CSV export
$7.99 once for Pro

Try before you buy

Every Pro control can be tried three times in the app, so you know it does the job first.

Bought it years ago?

If you bought Fourier, oScope or Octave before, Pro is already yours. Open the update on the same Apple Account.

No strings

No subscription, no ads, no account. Audio is analyzed on your device and never leaves it.

About the films

Every frame of every app is real.

Each film has its own piece of music. The music was played into the app in one continuous take, so what you see on the phone is the app drawing the song you hear: Fourier finding the harmonics, oScope locking the waves, Octave catching the bass, Soundscape spelling out words hidden in the overtones.

No mockups and no retouching inside the screen. The captions, the harmonic labels and the white touch rings sit on top.

Since 2009

Old instruments, rebuilt.

These began in 2009 as iPhone apps. In 2026 every one was rebuilt from scratch, with a shared C++ signal-processing core, low-latency native audio and Metal graphics, for iPhone and iPad.

  1. 2009oScope starts as an iPhone project: a continuous waveform, a triggered single shot, an FFT.
  2. 2010Fourier and Octave join it on the App Store.
  3. 2012A Soundscape prototype draws frequency history. It never ships.
  4. 2026All four rebuilt and free. Soundscape ships at last.
Help & support

Getting the most from the instruments

Getting started

Allow microphone access when the app asks. Analysis runs locally on your device. Settings includes a synthetic demo signal, so you can explore the controls without the microphone.

Is it really free?

Yes. Each app is free with no time limit: the live display, touch readouts, zoom and freeze. Pro is an optional one-time purchase per app. Controls marked PRO can each be tried three times; data export has no tries.

I bought the app before

Pro unlocks on its own when you open the update signed in to the Apple Account you bought it with. If it doesn't, open the Pro sheet and tap Restore Purchases.

Freezing, measuring, exporting

Tap Freeze to hold the display and Resume to return to live audio. Touch the spectrum, octave graph or spectrogram to measure a frequency. Triple-tap or use Reset to clear peaks or history. Keep › Export CSV saves the data (Pro).

Choosing response speed

Short FFT windows respond quickly; long windows show more detail at low frequencies. Narrow octave bands take longer to settle. Response depends on the device, microphone, display and audio route; Bluetooth can add a lot of delay.

Reading levels

Spectrum and spectrogram levels are peak dBFS; octave bands are RMS dBFS. These are digital signal levels, not calibrated sound-pressure measurements, so use them to compare shapes and changes rather than absolute loudness. Waveforms use full-scale amplitude.

Microphone troubleshooting

If the microphone is unavailable, open iOS Settings › Privacy & Security › Microphone and allow the app. Reconnect external audio hardware and restart capture from the app's Settings. Capture stops in the background and resumes when iOS allows it.

Support

Open a support issue with the app name and version, your iPhone or iPad model, the iOS version, the audio input and the steps that cause the problem. GitHub issues are public.

Press and creators

Films, icons and facts

Use any of these in coverage or videos. The films are 720p web copies of 1080 × 1920 masters, with sound.

Maker
Alex Wiltschko
Press
press@pocketinstruments.app
First released
oScope 2009; Fourier and Octave 2010; Soundscape 2026
Platforms
iPhone and iPad, iOS 17 or later
Price
Free; Pro $4.99 to $14.99 once per app
Privacy
No data collected; audio stays on the device