Theremin Synth vs Spectral Hold
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Theremin Synth
Create unique soundscapes with this multitouch synthesizer. Record, loop, and overdub your creations, then export them as WAV files to share. Experiment with various waveforms and effects for endless sonic possibilities.
- Multitouch synthesis
- Record, loop, and overdub
- Adjustable delay, feedback, and scuzz effects
- Four waveform options
- Export recordings as WAV files
- Offline functionality
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This is a multitouch synth instrument. Play it by touching and swiping the screen, changing the waveforms and sliding the effects to create anything from traditional sci-fi theremin sounds to deep scuzzy soundscapes. Use the looper controls to record, loop and overdub layers. Then if you wish to save or share your recording, hit the download button to send your wav file to other compatible apps like Messages, Email, Dropbox etc. The original Theremin went live in 2014 on the web at femurdesign.com/theremin. Over a million hits later and hundreds of requests for a record button, I have redesigned it. Now the Theremin is ready for you to experiment with. Happy playing! -- SPECIFICATIONS -- • Record, loop and overdub options. • Multitouch allows up to 8 tones to be played simultaneously with your fingers • 3 sliders: delay, feedback and scuzz • 4 waveforms: sine, square, triangle and saw • No internet needed, works both online and offline • Download the loop as a .wav file • Loops can be shared with other apps like Mail, Message and more. • 1000+ installs • Compatible with iOS versions 8 - 10 • Optimized for iPhone, iPad & iPad Pro -- REVIEWS -- Gizmodo "Just mess around! Twiddle those faders! Swipe and click with reckless abandon! Turn the volume all the way up, give the dog a panic fit, and make your neighbours think the street's being invaded by giant cabbage people from planet Zok. Trust me, this will never get old.” Dangerous Minds “New online theremin simulator kind of sounds cooler than the real thing. Check it out and annoy your co-workers.” Mashable “Messing around with this virtual theremin is completely addicting” -- CONTACT -- To find out about my other musical app projects, please go to femurdesign.com and share your loops with me on Facebook and Twitter. Facebook: facebook.com/femurdesign Twitter: @femurdesign For any queries and support contact me here: femurdesign.com/support
Spectral Hold
This audio processor analyzes sound in real-time, allowing you to tilt the frequency spectrum or freeze a moment into a sustained drone. Shape your audio with adjustable gain and pivot frequencies.
- Spectral tilt EQ
- Spectral freeze effect
- Adjustable pivot frequency
- Real-time audio analysis
- Dry/wet mix control
- Delay compensation
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SPECTRAL HOLD A spectral processor that combines a frequency-domain tilt EQ with a spectral freeze. Audio is analyzed with a short-time Fourier transform (1024-point FFT, 75% overlap, Hann window). Each frame's bins can be tilted around a pivot frequency, and the most recent frame can be frozen and held indefinitely, turning any moment of the input into a sustained spectral drone. ------ CONTROLS TILT Applies a spectral tilt around the pivot frequency. The gain of each bin is scaled by tilt * 3 dB per octave of distance from the pivot. Negative values darken the sound by attenuating highs and boosting lows; positive values brighten it by boosting highs and attenuating lows. At 0 the spectrum passes unchanged. Range: -1.00 to +1.00 (so +/-3 dB/octave at the extremes). PIVOT Sets the frequency around which the tilt rotates. Bins above the pivot are affected in one direction and bins below in the other; the pivot itself is left at unity gain. Lower the pivot to pivot the tilt around the low end, raise it to rotate around the highs. Range: 20 Hz to 20 kHz (exponential), automatically clamped below the host Nyquist frequency. FREEZE Captures and holds the most recently analyzed spectral frame. While engaged, the stored magnitude and phase of every bin are replayed on each hop instead of the live input, producing a continuous frozen texture. Tilt and pivot remain active on the held spectrum, so the frozen sound can still be shaped. Disengage to return to live processing. DRY/WET Blends the unprocessed (dry) input with the processed (wet) output. At 0% only the dry signal is heard; at 100% only the wet. The dry path is internally delay compensated so it stays time- and phase-aligned with the wet path at every mix setting, with no comb filtering. Useful for layering a frozen pad underneath the live signal, or easing in a tilt. ------ NOTE Because the effect works frame by frame, it reports a latency of one FFT frame (1024 samples, about 21 ms at 48 kHz) to the host for accurate delay compensation.
Screenshots
Verdict
The clearest difference is rating: Spectral Hold at 5.0 against Theremin Synth's 3.2. Spectral Hold also leads on price ($1.99 vs $2.99). Theremin Synth's advantage is ratings volume (6 vs 2) and iOS requirement (12.1 vs 17.0). On ads, in-app purchases, monetization model and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Theremin Synth costs $2.99 and Spectral Hold $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Spectral Hold holds the better App Store score, 5.0 against 3.2. Both are backed by a comparable volume of ratings — 6 and 2 respectively.
| Parameter | Theremin Synth | Spectral Hold |
|---|---|---|
| Price | $2.99 | $1.99 — better |
| Rating | 3.2 (6 ratings) | 5.0 (2 ratings) — better |
| Positive reviews | 63.6% of reviews | — |
| Number of ratings | 6 — better | 2 |
| Update frequency | Every 2 months | — |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 12.1 — better | 17.0 |
| Further details — not scored | ||
| Size | 1 MB | 7 MB |
| Age rating | 4+ | 4+ |
| Developer | Luke Phillips | Callback Audio, LLC |
Customer experience
Theremin Synth
Spectral Hold
In-app purchases
Theremin Synth
No in-app purchases
Spectral Hold
No in-app purchases









