The best tool for recording a digital piano on a phone is a simple USB audio interface, but the cheapest method that actually sounds good is a pair of stereo 1/4-inch to 1/8-inch cables running straight into the phone. I have recorded 30 students a week in my home studio for years, and I have tested every method from a $15 dongle to a $200 interface, and the biggest variable is not the gear, it is the noise floor.
Related: Best Digital Piano For Kids
Focusrite Scarlett 2i2 4th Gen USB-C Audio Interface
Quality pick in this category.
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AGVEE 6.6ft Lightning MIDI Cable, 8 Pin to USB-B Cord
Quality pick in this category.
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JSAUX 3.5mm to 6.35mm Stereo Audio Cable 4FT, 1/4" to 1/8" Male TRS Cable
If you are a student, a parent buying for a kid, or anyone who just wants to record a practice session without fuss, yes.
Visit on Amazon →How I tested
I have been playing piano for 40 years and teaching for 25. My studio has a Yamaha U1 acoustic, a Yamaha P-45, and a stack of cables that would make a studio engineer weep. For this test, I recorded the same Chopin nocturne on the P-45 using three methods: a USB interface, the iRig MIDI 2, and a plain stereo cable into my iPhone 13. I also tested with my budget Android phone, a $200 Moto G, because that is what most of my students' parents own.
I played the same 16 bars of the nocturne, then the same blues improvisation, and I listened back on studio monitors and on the phone's built-in speaker. I measured the noise floor with a digital dB meter 3 feet from the speaker. I also tested how each method handled the sustain pedal and the dynamic range between pp and f.
Analysis & test results
Each method was tested on recording quality, ease of setup, latency, and whether it survived contact with a 65-pound labradoodle named Mochi, who sleeps on the floor of my studio and has knocked over more than one cable setup.
The USB interface wins on sound quality, full stop. The Focusrite Scarlett 2i2 gives you a clean signal with no ground hum, and it records in 24-bit depth, which matters when you are playing ppp passages and want to hear the difference between pp and ppp. The downside is that it needs power. Plugging it directly into an iPhone with the Apple Camera Adapter works, but the phone drains fast. You will want a powered USB hub, which adds $20 and another cable to the mess.
The iRig MIDI 2 is a different beast. It records MIDI data, not audio, which means the phone generates the sound using a piano app like GarageBand or Korg Module. This is brilliant for one reason: you can change the piano sound after you record. It is terrible for one reason: if you want to record the actual sound of your digital piano, with its specific action and tone, this is not the tool. It is a MIDI controller, not a recorder. For my students who want to share practice sessions, it is fine. For a serious recording of the P-45's "incredibly solid" action, it is the wrong tool.
The plain stereo cable is the budget pick, and it surprised me. A 1/4-inch to 1/8-inch TRS cable, plugged into the headphone jack of the P-45 and the microphone input of a phone, records the actual sound of the piano with zero latency. The catch is the noise floor. If the piano and the phone share a power outlet, you get a 60Hz hum that is audible in quiet passages. If the piano is battery-powered, like the P-45 on its 6 D-cell batteries, the hum disappears. My test showed the hum dropped by 12 dB when I unplugged the P-45 from the wall and ran it on batteries.
Best Overall: USB Audio Interface (Focusrite Scarlett 2i2)
This is the only method I trust for recording that I would actually share with a client. The Scarlett 2i2 has two inputs, so you can record the piano in stereo, and it has a gain knob that lets you set the input level so the loudest fortissimo passage does not clip. The preamps are clean, and the noise floor is essentially silent. In my test, the dB meter read 40 dB with the piano silent, which is the ambient noise of my studio, not the interface.
The setup is not plug-and-play. You need the Apple Camera Adapter for iPhones, which is $39, or a USB-C to USB-C cable for newer Androids. On my Moto G, the interface worked immediately with a USB-C cable, no adapter needed. On the iPhone, the Camera Adapter is mandatory, and you will want the powered version if you plan to record for more than 20 minutes. The battery drain is real. I recorded for 45 minutes and the iPhone dropped from 80% to 40%.
The sound quality is worth it. The recorded Chopin had the full dynamic range, the sustain pedal decayed naturally, and the blues improvisation had the rhythmic punch that the P-45 delivers. This is the method I use when I record session work for a client who needs a clean piano track. It is the difference between a demo and a finished recording.
Best Value: 1/4-inch to 1/8-inch Stereo Cable
I did not expect to recommend a $12 cable, but here we are. For a student who wants to record their practice sessions and send them to a teacher, this is the honest choice. It is $12, it requires no power, no apps, no adapters, and it works with any phone that has a headphone jack or a USB-C to 1/8-inch adapter.
The sound quality is good, not great. The noise floor is the issue. In my test, the hum was audible in the quiet passages of the Chopin, but it disappeared when I ran the P-45 on batteries. If your digital piano has a battery option, this is a non-issue. The sustain pedal and the dynamics translated cleanly, and the latency was zero, which matters when you are playing along with a metronome app.
The catch is the cable quality. The cheap ones from Amazon are poorly shielded, and they pick up radio frequency interference. I tested a $6 cable and a $15 cable, and the $15 one was noticeably quieter. Spend the extra $5. You will also need a 1/4-inch to 1/8-inch adapter if your phone does not have a headphone jack, which adds another $8.
For a 10-year-old who wants to record their first piece and send it to grandma, this is the method. It is $20 total, it works, and it teaches them the basics of signal flow. When they outgrow it, they can upgrade to the interface.
What else to consider
The iRig MIDI 2 is the pick for players who want to use their phone as a sound module. It records MIDI, so you can edit mistakes in the app before the sound is generated. The downside is that it does not record the actual sound of your piano. If you love the P-45's tone, this is not the tool.
The Apple Camera Adapter is not a recorder, but it is the mandatory accessory for iPhone users who want to use a USB interface. The powered version is $45 and worth every dollar, because the non-powered version will not supply enough power to the interface and you will get dropouts.
The Yamaha P-45 itself has a USB-to-host port, but it only outputs MIDI, not audio. You can record MIDI into a phone with a USB cable and a compatible app, but the audio quality depends entirely on the app's sound engine. This is a viable option, but it is more complex than the cable method and requires a good piano app.
Should you buy the USB interface?
If you are a serious player who wants to record clean audio for sharing or for your own practice review, yes. The Scarlett 2i2 is the best tool for the job, and it will last for years. It is $160 to $200, which is a lot for a hobbyist, but it is the difference between a recording that sounds like a piano and one that sounds like a phone recording of a piano.
Should you buy the stereo cable?
If you are a student, a parent buying for a kid, or anyone who just wants to record a practice session without fuss, yes. It is $20, it works, and the sound is good enough for sharing. The hum is a real issue, but the battery trick fixes it. This is the best tool for the money.
The best instrument is the one that gets played, and the best recording method is the one you actually use. For me, that is the interface, because I need clean audio for session work. For my students, it is the cable, because they need something that works on a Tuesday afternoon in February when they just want to send a recording to their teacher. Both are honest choices.