Penbeat works especially well with music that meets one or both of the following conditions:

• A constant BPM

• Stem files are available

If the music has a constant BPM, you can synchronize it with loop-based audio.
If stem files are available, you can enjoy more dynamic performances by muting and unmuting individual tracks in Penbeat.

Our top recommendation is FL Studio. The free edition includes almost all of the features found in the full version, including tempo-adjustable drum loops and a tool that can automatically separate a single audio file into basic stems.
Although you cannot reopen saved projects in the free version, you can still export audio, making it more than sufficient for creating drum loops and mixing stems.
https://www.image-line.com/fl-studio/download

If you're looking for an easier way to get loop material, you can also try one of these online drum machines:
https://soundtrackloops.com/online-drum-sequencer/
https://drumbit.app/
https://patternsketch.com/
https://homestudio.genius.com/

Music distributed with stem files is still relatively uncommon. However, many VOCALOID producers make stems available for their songs.
https://scrapbox.io/musicstudyroom/%E3%82%B9%E3%83%86%E3%83%A0%E3%83%BBMIDI%E3%81%AA%E3%81%A9%E6%A5%BD%E6%9B%B2%E3%83%87%E3%83%BC%E3%82%BF%E9%85%8D%E5%B8%83%E3%81%AE%E3%81%BE%E3%81%A8%E3%82%81

(The VOCALOID Collection, currently taking place, is also offering stem files for many popular songs. Be sure to try them with Penbeat!)
https://vocaloid-collection.jp/stems/

There are countless websites offering sample packs such as drum loops. Here are some recommended resources:

Rhythm Lab Amen Breaks
https://rhythm-lab.com/amen_breaks/
https://rhythm-lab.com/amen_breaks_vol2/
https://rhythm-lab.com/amen_breaks_vol_3/
https://rhythm-lab.com/the-ultimate-amen-breaks-pack/

glitch with friends https://www.glitch.cool/projects

MusicRadar https://www.musicradar.com/news/tech/free-music-samples-royalty-free-loops-hits-and-multis-to-download-sampleradar

Cymatics https://cymatics.fm/

WavGrind https://wavgrind.com/

Ghosthack Audio https://www.ghosthack.de/free_sample_packs/

99Sounds https://99sounds.org/sounds/

(The tools and sample resources introduced above are intended for personal enjoyment. Please check the license terms of each resource before using them for other purposes.)

We are also considering releasing music DLC specifically designed for Penbeat in the future.

Thank you for your support, and we hope you continue to enjoy Penbeat!