It is difficult for me to distinguish among the vocalizing of John Mitchell, Joan Baez and Judy Collins when one of the three is introducing a new song on the radio.

All come across with sweet angelic voices that lean to city-folk music material and I find myself waiting for the finish and the DJ to announce which it was.

MISS MITCHELL was in Detroit last night playing to a full and enthusiastic audience at Masonic Auditorium.

Since it was a live performance, there naturally were no second takers or technical miracles from the studio people - just Joni, her six string and Masonic's near-perfect acoustics.

Sadly unlike Baez and Collins, Joni Mitchell proved to be the kind of vocal talent that requires the advantages of a recording studio.

As a writer, her melodies when recorded by other performers, such as Miss Collins, Crosby, Stills, Nash and Young and even Neil Diamond are distinct and richly-flavored.

But, last night, Joni's "Both Sides Now" sounded a lot like her "Circle Game."

Her vocal style of holding one note at the end of a measure and then suddenly jumping a full octave is interesting on record.

But live, her leap often lands flatly, missing the intended note completely.

Her poetry is for the most part well-contrived but at times she tends to cram too much lyric into a single stanza. As a result, it often comesoutsoundinglikethis.

She picks topical and commercially pointed subjects such as ecology ("They paved paradise and put up a parking lot"), harmonious existence among the young ("We are stardust, we are golden") and plenty of love lost and love regained.

In a new song aimed at jabbing the moguls of the recording industry she states: "I know I'm biting the hand that gives me (material) things."

And then she adds sadly: "But I can't afford to give it up yet."

She played three instruments last night, opening on guitar. Her scratch-and-pick style really should have been backed by at least a partial band.

She later turned to piano and played "Woodstock." It was a slower and more deliberate rendition than the version made popular by Ian Matthews.

Her third choice was an interesting and seldom used instrument called the dulcimer which is shaped somewhat like a small guitar and played face-up on the performer's lap.

The dulcimer is a form of zither and the strings are plucked, giving it a sound quite similar to that of a sitar.

JONI WAS PRECEDED to the stage by Jackson Browne, another in a long line of writers who is trying to become a singer, but should stick with writing.

His set might have been passable in a small folk club in Peoria but, in a 4,600-seat concert hall in Detroit, it was inexcusable.

At one point, he played a song with his guitar completely out of tune. He tried to remedy the situation afterwards, but when he unsuccessfully attempted to tune a high "E" string, he gave up and turned to the piano.

The crowd brought him back for an encore which really got him in trouble.

It seemed the tune he had just played was the only one he knew on piano and he was forced to again try to tune the six string.

He finally began after working with the instrument and bringing it up to only slightly out of tune, but he forgot the words to his own song.