The world's most popular music channel isn't iTunes, Spotify or Radio 1 – it's YouTube. 300 hours of video are uploaded to YouTube every minute, and much of that video is music – but it's music in a format that isn't ideal for listening to on portable devices such as smartphones or iPods. That doesn't mean you can't download it or change the format, however.
What you need to know about music files and quality
When you use a service such as ClipConverter, as we'll do in this tutorial, you'll be given a choice of different file formats and settings for the music file you'll create. The options you choose here will affect what devices you can play your music files on, and they can also affect how good the end result will sound.
ClipConverter offers three music options: MP3, M4A and AAC. MP3 runs on almost anything from computers to smart car stereos, and it'll play happily on iPods and smartphone music players too. However, it's a fairly old format and it's not as efficient as more modern music standards, which can store higher quality music in the same amount of space.
ClipConverter's other options, M4A and AAC, are two of those standards. They're widely supported too, but you might find that they won't play on some devices such as USB-enabled car stereos. If they are supported, use them over MP3: they don't include copy protection, and at the same quality settings they sound noticeably better than MP3 files do.
Once you've chosen your format, the next step is to decide what bitrate you want. The bitrate is literally how many bits per second the file format uses – the more bits, the higher the quality. Music file bitrates are measured in kilobits per second, or kbps for short, so an MP3 with a bitrate of 256kbps should be twice as good as an MP3 with a bitrate of 128kbps. And that's largely true, because MP3 uses what's called "lossy" compression.
Lossy compression: what it is, and when it's good
Lossy compression is based on a simple idea: a computer analyses the music and gets rid of anything it decides isn't important. That massively reduces the amount of space a music file takes up – compared to CD quality music files, an MP3 file is roughly one twelfth of the size – but the more you throw out, the poorer the quality becomes.
An MP3 file encoded at 320kbps sounds almost indistinguishable from the original, but the same music at 128kbps is noticeably poorer. Unless you're using really bad headphones or speakers, 128kbps MP3s will sound pretty horrible compared to the rest of your music.
Choosing the right bitrate for YouTube music
Watching a black and white film on a colour TV doesn't magically colourise it, and whacking your audio converter's settings up to maximum bitrates won't magically improve the sound quality of a YouTube video if the original isn't up to snuff.
In most cases, the music you'll hear on a YouTube video is an AAC stream of 128 to 192kbps – even though YouTube recommends that video uploaders use a bitrate of 384kbps for stereo audio. That may be for future-proofing, or it may be to get the best results from Google's own music compression, but either way it means there's little point in going beyond 192kbps when you create M4A/AAC files, or around 256kbps for MP3s.
Is downloading music from YouTube legal?
That's a very good question. It's certainly against YouTube's terms and conditions, which say you can only use its content for streaming, and you could argue that it's unethical too: many artists depend on YouTube's ads for their income, so any ad-free playback you do is depriving them of income.
We suspect the legality of this is similar to ad-blocking – content owners would really rather you didn't do it and try their best to stop the tools from working, but there's not a lot they can actually do to prevent you listening ad-free if your listening comes under "fair use" in copyright terms. Then again we're not lawyers, so proceed with this at your own risk.