blips in loops

learning that crossfaders adjust volume in order to seamlessly loop samples, i edited my own loop with the pitch envelope tool.
i got the volume to be the same at the seams, but i’m still hearing the blips.
why does this happen?
the sample i’m working on is a cello single note.

You’ve picked a really hard example.
The problem is that during the course of a 'Cello note, the amplitude and timbre (frequency content) change. In order to create a seamless loop the ends must match up precisely, which is a matter of achieving a smooth transition of the waveform so there is not a sudden jump (click), and the amplitude needs to match, and the timbre needs to match.

I presume that the “single note” is just a few seconds? If so, please post it as an attachment (WAV of FLAC format) and you may get some practical suggestions of how to approach the task.

I presume that the aim is to produce a seamless loop that can loop round and round forever?

To add an attachment to your post, use the “upload attachment” feature below the message composing box. The maximum file size is 1 MB I think.

but i’m still hearing the blips.

Are you looping inside Audacity? If you’re not, some audio file formats loop a lot better than others.

Something else that isn’t obvious until you hit it. Are you the player? When you impress gentle vibrato during play by jiggling your left hand, those hand movements have to loop match, too. Suddenly it got a lot more interesting.

If it’s not critical, you can sometimes force a quick cross-fade instead of a cut and smoosh right over the fact you didn’t get a perfect match.

Someone in the Video wanted a brief video clip to loop perfectly at the intro to a DVD. You know, when they say “Play Movie,” “Chapters,” “Language,” etc. Those backgrounds never loop perfectly, but for some reason, some disks seem to work.

I asked them how long they were ever stuck on that screen before they watched the movie? Ten seconds? Make your own careful, perfect loop collection on the timeline over ten seconds and export that loop collection as one movie. Nobody will be around long enough to see the glitch.