Loop Trainer

Open a song you have and change its key and tempo freely: the speed (50–150%) keeps the pitch, and the key keeps the tempo. Pick any section and it loops, snapped to the beat. Loops and settings are saved for each song.

No file open

MP3, AAC (m4a), WAV, and more. You can also drop a file here. Files are never uploaded.

0:00.0 / 0:00.0
Speed100%
Key±0
Loop–

The pitch stays the same. Below 50% the sound breaks up, so 50% is the lowest.

Key

In semitones, up to ±6. The tempo stays the same, and it works together with the speed.

Beats and bars
Tempo
Beats per bar
Bar starts

Speed up on every loop
Start at
Each loop
Up to

Count-in before each loop
Clicks

Saved loops for this song

    Save loops such as “Intro” or “Solo, first half” and jump back to them any time.

    Space play / pause　↑↓ speed ±1% (Shift ±5%)　←→ move A by a beat (Shift move B)　Esc cancel moving a flag　A B set A / B here　L loop on / off　Enter back to A　- + key　Z zoom to loop / whole song　Ctrl+wheel zoom　Shift+wheel scroll　O open file

    Change the key and tempo freely, and loop any section of a song

    Loop Trainer is a free practice player for learning songs by ear. Open an audio file you have, drag over the waveform to choose the part you want to learn, and it repeats that part as many times as you like. The app finds the beats of the song, so the loop points snap right onto the beat. Slow it down to 70% or even 50% and the pitch stays the same, so you can hear every note of a fast guitar solo and play along in the original key.

    Speed up a little on every loop

    Turn on “Speed up on every loop” and the loop starts slow, then gets a little faster each time it comes around: for example 70%, 72%, 74% … up to 100%. You practise the phrase slowly first and reach the real tempo without stopping to change anything. A count-in can click before each loop so you have time to get ready.

    Speed and key for the whole song, saved loops

    You can also simply change the speed or the key of the whole song and listen or play along, without a loop. Shift the key up or down by up to six semitones, together with the speed. Tune to a song recorded a half step down, or move it to fit your voice. The loops, speed, and key are saved for each song in your browser, and you can keep several named loops per song, such as “Intro” and “Solo, first half”. Open the same file next time and you pick up where you left off.

    Files stay on your device

    The audio is decoded and processed only in your browser and is never uploaded. It works with MP3, AAC (m4a), WAV, and other formats your browser can play, on a computer, tablet, or phone. Music from streaming services (Apple Music, Spotify, YouTube) cannot be opened. No sign-up is needed.

    Guides

    How to use

    1. Open a song – Tap “Open file” or drop an audio file on the waveform. MP3, AAC (m4a), and WAV work in every browser. Music from streaming services cannot be opened.
    2. Choose the loop – Drag across the waveform. To move a flag, tap A or B (it turns blue) and then tap where it should go, or long-press it and drag. While it plays, “A” and “B” set them at the current position. ◀ and ▶ move them to the previous or next beat.
    3. Zoom the waveform – Pinch with two fingers to stretch or shrink the waveform, and move two fingers sideways to scroll. On a computer, use Ctrl + wheel (or pinch on the trackpad) and Shift + wheel. “Zoom to loop” fits the loop to the screen; press it again to see the whole song.
    4. Beats and bars – The app finds the tempo and the beats of the song (♩ ≈ 120 means about 120 BPM), and the loop points snap to the nearest beat. Turn on “Snap to bar starts” to snap to the first beat of each bar instead (◀ ▶ then move by a bar). Bar starts are guessed, so move them with ◀ ▶ under “Bar starts” if they are off, and set the beats per bar for songs in 3/4 or 6/8. If the tempo looks twice too fast or too slow, use ½ or ×2. Turn off “Snap to beats” to place the points freely (◀ ▶ then move by 0.05 seconds).
    5. Slow down – Set the speed between 50% and 150% with the buttons or the slider. The pitch does not change.
    6. Change the key – Move it up or down in semitones (up to ±6). The tempo does not change.
    7. Speed up on every loop – Turn it on and set where to start, how much to add each loop, and where to stop. It goes back to the first speed when you play from the start of the loop.
    8. Count-in – Clicks play before each loop. Enter the song's BPM (at 100%) or tap it in; the clicks follow the current speed.
    9. Saved loops – “+ Save this loop” adds the current loop to the list. Give it a name, and tap its time to go back to it. Everything is saved for each song and comes back when you open the same file.

    Read the full guide →

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    © 2026 ktkwmr · Licensed under the MIT License · About this site · Audio processing: SoundTouchJS (LGPL-2.1, loaded unmodified from jsDelivr)

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