I'm Yours: key, vocal range, and how hard it is to sing
Jason Mraz's I'm Yours is a ukulele-and-guitar pop standard people still look up for key, vocal range, and whether they can sing it. This page uses a measured vocal line from the recording: range D#3–G#4 (17 semitones), tessitura mostly B3–D4, phrasing tempo about 70 BPM, medium difficulty, longest note C#4 held 4.2 seconds, about 0.6 notes per second, duration 222 seconds. The commonly cited original key is B major.
The track sits in a conversational pocket rather than a belt-heavy chorus. That is why karaoke singers pick it, and why the same numbers still trip people who treat it as a throwaway campfire tune.
What makes it easy or hard to sing
Medium difficulty here is not a mystery. The span is 17 semitones from D#3 to G#4. Most of the line lives between B3 and D4, so you spend minutes around the speaking-to-head-voice break for many male voices and in a comfortable midrange for many female voices who drop an octave or stay in chest. The top G#4 is not a scream note, but it arrives after long, talky phrases, so fatigue shows up as pitch sag rather than as a missed high C.
Phrasing tempo is about 70 BPM with 0.6 notes per second. That is not a melisma workout. The challenge is breath across long, speech-like sentences at a relaxed groove. If you rush the groove you run out of air before the line lands; if you drag it, the 4.2-second C#4 (the longest measured hold) feels endless and the pitch wobbles. Duration is 222 seconds, so you need enough stamina to keep B3–D4 in tune for the full length without the tessitura climbing.
The low D#3 asks for a supported chest or mix that does not collapse into fry. Singers who live only in a bright mix will undershoot those bottoms. Singers who live only in heavy chest will find G#4 thin unless they mix earlier. Medium difficulty, in these numbers, means coordination across a moderate span at a moderate density, not extreme range or speed.
Who it suits
The measured range D#3–G#4 and the B3–D4 center fit baritones and lower tenors in the original key. High tenors may feel underused until G#4 and should watch the D#3. Mezzo-sopranos and altos can sing it as written if the low D#3 is reachable; many sopranos will want a higher transposition so the tessitura is not stuck in a weak low-middle. The 4.2-second C#4 is a midrange sustain, not a high money note, so voices that crack only at the top often still fail here from breath and intonation.
If your comfortable chest sits below B3, the original key is a natural fit. If your break is right on C4–D4, plan mix work on the phrases that sit in that band for most of the song.
How to practice it
Map your own lowest and highest notes against D#3 and G#4 before you sing full takes. If D#3 is a stretch, do not fake it with fry; drop the key until the bottom is clean, then work back up. If G#4 is the limit, keep the original key and practice mixing on short fragments rather than pushing chest.
Work at the measured ~70 BPM. Speak the rhythm on a single pitch first so the 0.6 notes-per-second density feels like conversation, then add pitch. Mark breaths before the long C#4 hold (4.2 seconds) so you do not arrive empty. Keep that hold on a stable vowel; do not swell so hard that the pitch sharp-sags.
Split the 222-second duration into phrase groups. Repeat the B3–D4 pocket until it stays in tune without listening for the guitar. Then add the D#3 bottoms and G#4 tops as separate drills. Medium difficulty means you fail from sloppy breath and register shifts, not from missing circus notes, so record short loops and check those two faults.
Upload the song to PitchHighway and learn it phrase by phrase.