With digital music, there is a trade-off between music quality (see high fidelity) and file size. The higher the quality, the larger the file size. In planning your music library, there are 2 things you need to consider before starting:
- How do you plan to enjoy your music?
- How much storage do you have in your music player?
If you're going to enjoy your music in a proper music listening environment with good speakers, you will probably want the highest fidelity recording. For this, you would use either vinyl records or audio CDs. This are LOSSLESS recordings, meaning that ALL of the sound made during the recording was transferred to the storage medium.
If you're planning to listen to your music with your MP3 player's speakers, or with low-cost headphones, or in a moving car with the car's sound system, you can probably be satisfied with music that's a "good enough" rather than a perfect.reproduction. To reduce the size of the song's digital file, there are LOSSY formats and these include AAC and MP3. These formats don't include all of the original audio information, which allows much smaller file sizes but still sounds very much like the original recording. Some MP3 player devices do not have expandable storage through SD cards so even a small number of high quality songs can fill up the available storage space.
Once you've decided upon your music format (AAC, MP3, etc), the SAMPLING (ie, BIT RATE) allows you to trade-off fidelity against file size. Basically, the music's sampling is how many "slices" of your music is used in your file. Each slice of digital music is comprised of ones and zeros (audio bit depth) and the greater the BIT RATE, the more accurately the music will be reproduced. Common MP3 bit rates for mobile devices are 128 kbit/s, 160 kbit/s, and 192 kbit/s. I use 192 kbit/s for my music library because my intent is to use my car's speaker(s) for playback and I have a 32 GB SD card. If your device has limited storage, use a lower bit-rate like 128 kbit/s.
Even though a device's owner's manual officially states the maximum capacity SD cards (see Secure Digital) that are supported (like 32 GB for my Moto G), often larger capacity SD cards (like 64 GB or 128 GB) will still work. Check your device's support forum to see what experiences others have had with SD cards. While the speed of an SD card for music playback is less crucial than for video recording, get the fastest SD card your device will support. SD cards with Class 10 (10 MB/s) speed ratings are common now and support full HD (1080p) video recordings.