Instructions for recording vocal music on mobile phones

Recording app

Some good, recommended apps are:

1. Audio Recorder:

https://play.google.com/store/apps/details?id=com.dimowner.audiorecorder&hl=en_IN

2. Audio Recorder:

https://play.google.com/store/apps/details?id=com.github.axet.audiorecorder&hl=en_IN

(yes, both have the same name)

These are both free, simple in design, lite and contain no advertisements. They also allow the

user to adjust recording settings. Recommended settings for good quality recordings are:

Sample rate: 44.1 kHz

Format: Wav or MP3

Channel: Mono

Although the default sound recording app in most new smartphones might work well too,

sometimes they could apply unwanted filtering to limit the audio bandwidth to the human audible

range (figure 2 below).

Microphone

The onboard microphone of a phone, especially if it’s a recent model, is often better suited for

music than the microphones present in earphones or headphones.

Most earphone/headphone mics are usually designed for speech and hence tend to apply filters

to compress the audio bandwidth (figure 3 below). However, these can be better at not picking

up background sounds, while onboard phone microphones tend to capture faint background

sounds too.

Earphones manufactured recently by a good audio tech. company could have good

microphones, but the ones that are shipped with mobile phones are generally not.

Note



: If the phone is an old, budget model, then its onboard mic is likely to be poor, and neither

using good quality earphones nor a good recording app can give good recordings. It is best to

use a different device in such a case.

Place the phone mic neither too close to nor too far from the singer’s mouth. About 3/4

th

- 1 foot

away is good. Most phones have the mic at the bottom so keep the phone with its bottom

pointing towards the singer. If unsure about the mic placement in the phone, it should be easy to

find in the user manual or on the internet by looking up the model name.

To avoid signal saturation or clipping, try to move slightly away from the mic while singing loud

phrases.

Recording environment

Ensure that it is quiet around you when recording, especially when using the phone’s onboard

mic. If possible, try not to record in a room that is too empty - that can add unwanted

reverberation to the recording. And needless to say, switch the phone to the silent mode.

While earphone microphones can give cleaner recordings with relatively lesser background

noise, they also tend to filter the audio. Hence it is better to ensure a quiet environment and use

the phone’s mic.

Some common noise sources to look out for: clock with a loud seconds hand, running fan, open

window, a loud motor running outside.

Using a tanpura / metronome app for reference

Use another device to play the tanpura / metronome and listen to it over earphones, but keep its

volume low to avoid the risk of the recording mic picking that up.

Spectrogram images of some recordings (generated using librosa and matplotlib on python)

1. A good recording with full bandwidth and no filtering

2. Empty region from 20 - 22.050 kHz for an audio sampled at 44.1kHz indicates abrupt

bandwidth clipping

3. Filtering by an earphone mic - signal severely attenuated beyond 5kHz