spool. vs HarmonyAngel
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
spool.
Create full songs on your phone with this pocket music studio. It offers a variety of sound engines, sampling capabilities, step sequencing, and a 4-track tape recorder for recording and mixing your music. Effects and MIDI controller support enhance the creative process.
- Multiple sound engines
- Sampling and sequencing
- 4-track tape recording
- Extensive effects rack
- MIDI controller support
- Step sequencer
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Make a whole song on your phone. Spool is a pocket music studio inspired by the joy of hardware grooveboxes — play, sample, sequence, and record to tape, all in one playful instrument. Fourteen sound engines. From punchy FM and fat subtractive Pulse to shimmering Cluster, plucked String, granular Cloud, the TALK vocoder, the WIDE stereo engine, THUMP bass, a Sampler, and two drum machines — each with its own animated, touchable visualizer and four hands-on controls. Sample anything. Record straight from the mic into the sampler or drum kits, trim it, and play it across the keyboard. Drums & beats. Build kits, chop a sample into a playable kit, and lock in grooves with the step sequencer. Playful sequencers. Pattern and arpeggiator to start; unlock Stream, Taps, and the bouncing-ball Gumball machine for happy accidents. Six minutes of 4-track tape. Record, overdub, varispeed (including reverse), scrub, and bounce your jam to a finished mixdown — export to WAV. Your tape is saved with your project. Effects & mixer. A deep rack — delay, spring reverb, drive, compressor, chorus, multimode filter, phaser, tremolo/auto-pan, beat-repeat stutter, and a pitch-shifter/harmonizer — many tempo-syncable. Plus a master EQ and brickwall limiter so it always sounds finished. Plays with your gear. Connect a USB or Bluetooth MIDI controller and play Spool like hardware. AUv3 plugin support is planned for a future update. Free to download and make music with a starter set of engines and sequencers. A single one-time Spool Pro purchase unlocks the full instrument — all engines, sampling, every effect and sequencer, unlimited projects, export, and MIDI. No subscription. Spool is an original, independent work by a solo developer — affiliated with no hardware maker.
HarmonyAngel
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HarmonyAngel is a MIDI and vocal harmony processor for musicians who want one monophonic line to follow the active chord. Choose chord slots on two performance pages, then play from a MIDI controller or the on-screen piano. For every incoming note, HarmonyAngel can generate descending chord tones below it, align voicings to a chord root, preserve slash-chord roots, and forward aftertouch to the generated harmony. Turn on Mic Input to sing into HarmonyAngel. The app performs low-latency monophonic pitch detection locally, uses the detected note to create the same chord-aware MIDI harmony, and provides a live tuner and input-level meter. Premium users can optionally hear pitch-corrected lead vocal and pitch-shifted vocal harmony audio, with selectable pitch detector, pitch shifter, formant, latency, buffer, trigger-level, and trigger-velocity controls. Choose a Jazz Soli style when you need arranged ensemble-style lines instead of simple chord stacking. Built-in Bebop, Smart Soli, Smooth Big Band, Functional Jazz, Barry Harris, Cool Jazz, Quartal Fusion, Minimal Guide Tones, and Altered Dominant styles use the active chord, melody direction, and musical register to produce practical voicings. Premium users can create, validate, import, export, and organize declarative custom styles in the Jazz Soli Library. Use it standalone with CoreMIDI and the built-in sine synth, or load the AUv3 MIDI processor inside a compatible host. Page controls, progression stepping, hold behavior, custom chord types, selectable MIDI ports, channel routing, keyboard range, display transpose, and velocity shaping are available from the performance UI. Highlights: - Two pages of 12 editable chord slots with no-harmony slots - Built-in chord types, slash roots, and named custom chord types - Jazz Soli styles for melody-aware, multi-part jazz voicings - Premium Jazz Soli Library authoring with validated import and export for custom styles - One-page or two-page MIDI control channel slot switching - Progression controls for stepping through saved chord sequences - Full or partial on-screen piano with touch velocity and aftertouch - Harmony count, root alignment, skip-first-harmony, and revoice-on-switch controls - Delta or ratio harmony velocity and aftertouch shaping - Mic Input with local monophonic vocal pitch detection, tuner, and input-level metering - Premium pitch-corrected lead vocal and pitch-shifted vocal harmony audio - Premium single-channel or rotating-channel harmony MIDI output - Premium MIDI input/output port selection and virtual MIDI output port - Hold and panic controls with process/bypass hold modes - Premium AUv3 MIDI processor extension with preservable host state - Optional built-in sine wave synth for quick testing or standalone use HarmonyAngel is designed for keyboardists, singers, composers, producers, worship musicians, live performers, and anyone who wants fast chord-aware harmony from simple MIDI or vocal input. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://bwinnovationtw.github.io/apps/harmonyangel/privacy.html
Screenshots
Verdict
spool. and HarmonyAngel are too close to call on the numbers: across 5 compared parameters — price, ads, in-app purchases and device support among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. spool. sells 1 one-off in-app purchase and HarmonyAngel sells 4 in-app purchases, starting at $0.99 per 7 days. Whichever you choose, the download price is not the number that matters.
| Parameter | spool. | HarmonyAngel |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (9 ratings) — better | — |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 9 — better | — |
| Update frequency | — | Every 4 weeks |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 17.0 | 17.0 |
| Further details — not scored | ||
| Size | 2 MB | 7 MB |
| Age rating | 4+ | 4+ |
| Developer | Kristopher Yang | PING YAO WANG |
In-app purchases
spool.
- Spool Pro$9.99
HarmonyAngel
- Weekly Subscription3 Days trial$0.997 Days
- Monthly Subscription7 Days trial$1.991 Month
- Yearly Subscription14 Days trial$9.991 Year
- Life-time Purchase$19.99





